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BIOLOGY TERM 1 NOTES: ANIMAL PHYSIOLOGY
Stages of Digestion
- DIGESTION is the process of breaking down food we eat so that it can be absorbed and
assimilated
...

1
...

2
...
It occurs in both the mouth and
stomach
...
CHEMICAL DIGESTION is the breakdown of large complex molecules into small soluble
molecules that can be absorbed by blood
...
ABSORPTION is when the small molecules are taken through the cells of the intestines
(digestive system) and pass into the bloodstream
...
ASSIMILATION occurs when the products of digestion are used for metabolic processes,
energy, growth, repair and reproduction or stored by body cells
...
EGESTION is the removal of indigestible material from the body as faeces
...

- Has an outer SEROUS COAT
...

- SUBMUCOSA contains blood vessels, lymph glands and absorbs nutrients
...

The LUMEN is where the food is
...



Peristalsis
- In PERISTALSIS, the longitudinal and circular muscles work in tandem to cause wave-like
contractions that move food down the alimentary canal
...

SALIVA is important because:
• It contains amylase (ptyalin) which breaks down starch
...

• It contains LYSOZYME an amylase, that breaks down carbohydrates remaining on the
teeth, preventing decay
...

• Chemicals in saliva help the taste buds detect food
...
5 litres of saliva is produced a day
...

The movement of the bolus is assisted by lubrication, resulting from the mucus produced by the
cells lining the oesophagus
...

• Trachea is pulled back to close the opening
...

The OESOPHAGUS is the tube that connects the mouth to the stomach
...

Starch digestion continues until the food enters the stomach (where the amylase is neutralised by
the acid environment)
...

- Once the food enters the stomach:

-

-

-

• Circular muscles contract to produce further peristalsis
...

• The food is mixed to produce CHYME
...

• Neutralises alkalinity of the bolus, deactivates amylase
...

• Dissolves minerals
...

The food leaving the stomach contains fats (unchanged), sugars (unchanged), maltose (formed by
amylase acting on starch), coagulated milk protein, polypeptides (formed by pepsin acting on
proteins), starch (not yet acted on amylase), protein (not yet acted on by pepsin)
...

The CARDIAC SPHINCTER is at the junction of the oesophagus and the stomach and is a
tight ring that opens and closes to allow food into the stomach
...


Small Intestine & Pancreas
- The SMALL INTESTINE has three distinct areas: duodenum, jejunum, ileum
...
This increases the
period of digestion and absorption to between 2 and 5 hours; site of chemical digestion
...

- Pancreatic juices are secreted via the pancreatic duct from the PANCREAS
...

• Proteases which continue the digestion of protein
...

• Lipases which act on the EMULSIFICATION (breakdown of fats) caused by bile to
digest fats into fatty acids and glycerol - ready for absorption
...

- Bile contains ORGANIC BILE SALTS which react with fat-soluble vitamins (A, D, E, K) and
cholesterol
...

- Salts emulsify fats and oils by reducing surface tension, producing an emulsion of small droplets
that has an increased surface area over which fat-digesting enzymes can work
...

- Are all reabsorbed in the small intestine and reused
...

- The ILEUM serves as a digestive and absorptive organ where molecules diffuse into
bloodstream
...

- The inside of the small intestine is folded many times to produce finger-like projections called
VILLI that increases the surface area over which absorption can occur
...
Each villus is 1mm in length
...


- The blood vessels and lacteals absorb the products of digestion where they are transported to the
-

-

liver
...

Movement of substances from the villi to the blood is assisted by muscular contractions
...

The large intestine is composed of the COLON: ascending, transverse, descending and sigmoid
...

Material is stored up to 36 hours in the colon, the semi-solid residue called FAECES is
discharged through the RECTUM, via the anus, which stores stools
...

- They are proteins that are folded into complex shapes that allow smaller substrate molecules fit
-

-

into them, known as the ACTIVE SITE
...

If the shape of the enzyme changes, its active site may no longer work as it has been
DENATURED by high temperatures or extremes of pH
...

• Chemical reaction is bi-directional
...

• Posses active sites for interaction with substrates
...

Enzymes are most active at optimum pH levels and rate of activity decreases outside optimum
levels
...

Enzymes are inactive at very low TEMPERATURE
...

Enzyme most active at optimum temperature; rapidly decreases beyond this
...

ENZYME CONCENTRATION increases rate of reaction until number of substrates becomes a
limiting factor
...


Liver
- The LIVER receives practically all the food absorbed by the intestine
...

Regulates the amount of food that reaches body cells
...

Regulation of amino acids and proteins: DEAMINATION is known as getting rid of excess
amino acids by removing the nitrogen component, the amino group which is poisonous, liver
concerts it into urea and goes to the kidney to get rid of (urine)
...

Purification of blood: poisonous substances produced by metabolism and disease-causing
organisms, drugs and alcohol
...

HEPATIC PORTAL VEIN transports glucose, amino acids, fatty acids, vitamins and minerals
...

Production of bile: the liver excretes bile produced during the breakdown of ‘old’ worn out red
blood cells
...

HEPATIC ARTERY supplies liver with oxygen
...
The glucose level in
the blood needs to be kept fairly constant
...

- GLYCOGEN is hundreds of glucose molecules joined together and some is stored in the
muscles
...

- INSULIN is made in cells in the pancreas called the ISLETS OF LANGERHANS
...

- The insulin enters the blood directly and is carried to the liver
...

- Insulin stimulates formation of glycogen and is secreted from the pancreas, which increases
circulatory insulin, uptake of glucose by cells and thus a decrease in blood glucose
...
RAPID (SECONDS): increases transport of glucose, amino acids (among the amino
acids most strongly transported are valine, leucine, isoleucine, tyrosine and phenylalanine)
and potassium into insulin-sensitive cells
...
INTERMEDIATE (MINUTES): stimulates protein synthesis (insulin increases the
formation of new proteins), activates enzymes that store glycogen, inhibits protein
degradation
...
DELAYED (HOURS): increases proteins and other enzymes for fat storage
...


Circulatory System
- CIRCULATORY SYSTEMS are arranged so that material within a circulatory vessel can

-

-

-

exchange substances with the cells that surround it
...

CLOSED CIRCULATORY SYSTEM is where circulating blood is enclosed within a system of
vessels
...

Circulatory systems contain a number of important components:
1
...

2
...

ARTERIES carry blood away from the heart
...

SYSTEMIC VESSELS carry blood to and from the body tissue
...


- The function of the HEART is to continually pump blood through the circulatory system by
-

rhythmic contraction and dilation
...

CORONARY ARTERIES form a network of vessels around the heart and supply the cardiac
tissue with oxygen and nutrients (i
...
glucose)
...



- VALVES separate atria from the ventricles and allow the flow of blood from atrium to ventricle
-

-

-

only
...

As the ventricle contracts, blood is pushed into the arteries
...
This pressure is created by the semi-lunar valve preventing back flow
...

DIASTOLE is when the ventricles relax and the arterial walls return to their normal position
...

Arterial contractions together with the pressure created by ventricular contraction force blood
around the body
...

- The inner membrane (ENDOTHELIUM) is one cell thick and is surrounded by a thick layer of
-

-

muscle and elastic fibres
...

When ventricles of the heart beat, blood is forced into the arteries under high pressure
...
The elastic walls, along with muscles, then return to their
original position, thus forcing blood further away from the heart
...

Arterioles continue to ‘thin out’ until only the endothelium remains
...

Narrower lumen to maintain high pressure surrounded by a thick wall made of two layers
...

Outer layer contains collagen that prevents the artery from rupturing due to high pressure blood
flow
...

Have a very wide lumen to keep pressure low and allows greater flow of blood
...

Have valves to prevent blood pooling at extremities (arteries do not have valves)
...

Muscular walls do not contract, thus blood flow back to the heart needs to be assisted
...


-

CAPILLARIES are involved with material and gas exchange with the surrounding body tissue
...

Wall is made up of a single layer of cells to allow for ease of diffusion
...

Form a dense network called CAPILLARY BEDS (sites at which exchange of substances
occur)
...

Capillaries on the venous side of the capillary bed gradually thicken until they become veins
...

If the fluids remained in the interstitial tissues, swelling would occur
...

Has valves but they are blind ended
...

The LYMPHATIC SYSTEM is an open system that plays a vital role in maintaining osmotic
and fluid balance in the tissues
...

The excess fluid is often plasma which is forced out of the capillary wall under pressure
...
The remainder is returned to the blood system by the
lymph system and is now called a LYMPH
...

Lymph vessels pass through lymph nodes that add lymphocytes to the lymph fluid
...


Blood & Blood Clotting
- Human has 5 litres of blood
...

Consists of plasma (55%), red blood cells (erythrocytes), white blood cells (leukocytes) and
platelets
...

Composed of water (90%), salts, amino acids, glucose, vitamins
...

Consists of GLOBULIN for body defence
...

ERYTHROCYTES are produced in bone marrow
...

Dead ones are removed from circulation by the liver and spleen
...

Lose nucleus and DNA in order to have more room for haemoglobin
...

Erythrocytes contain the protein HAEMOGLOBIN (Hb) which combines with oxygen to form
OXYHAEMOGLOBIN (HbO)
...

Red blood cell transport carbon dioxide from the body cells to the lungs
...


- LEUKOCYTES are white blood cells that are produced in the bone marrow and lymphatic
-

tissue
...

Protects against bacteria, produce antibodies, repair tissues
...

PLATELETS are produced from bone marrow when bits of cytoplasm pinch off from larger
cells within the marrow
...

Play a major role in blood clotting
...

Thromboplastin in the presence of Ca2+ ions causes the protein PROTHROMBIN to change
into THROMBIN
...


Respiratory System
- RESPIRATORY SURFACES displays the following characteristics:
• They have a large surface area
...

• All are moist because oxygen and carbon dioxide can only diffuse in solution
...

• Good ventilation, the respiratory surfaces need to receive a steady flow of air or water
...
This maintains a high concentration gradient across the surface of exchange
...
The membranes of the nasal passage
-

-

humidify the air
...

GOBLET CELLS secrete mucus, which moistens the air and traps airborne dust and bacteria
...
This is swallowed and any potential
pathogens are destroyed by stomach acid
...

The air is then drawn into the TRACHEA, which runs from the larynx to the lungs
...

At its lower end, the trachea divides into the left and right BRONCHI
...

The bronchial tree terminates into the ALVEOLAR DUCTS
...
Alveoli are the point of gas exchange
...


- GAS EXCHANGE is the exchange of oxygen and carbon dioxide in the alveoli and the
bloodstream; it occurs passively via diffusion
...


- ALVEOLI are made of single layer of flattened cells (thin wall) so diffusion distance is small
...

- Increased SA:V ratio: high numbers of spherically-shaped alveoli optimise surface area for gas
exchange
...


Notes
Insects

- Air enters the

-

-

Fish

respiratory
systems of insects
through a series of
external openings
called spiracles
...

Spiracles allow
oxygen to pass
into the body,
regulating
diffusion of cabon
dioxide
...

Highly
vascularised
internal gills
...

The result is that
water is drawn out of
the tracheoles, which
has the effect of
opening up these air
passages
...


- Water vapour also
passes freely through
open spiracles; water
retention is
particularly difficult
for small insects with
relatively high SA:V
ratio
...

Countercurrent
circulation
...

!

!
Frogs

- While completely

-

-

Mammals

submerged,
respiration takes
place through the
skin
...

Breathes using
lungs by taking air
in through their
nostrils
...


- Only requires
smaller lungs as it
uses its skin as a
respiratory surface to
breathe as well
...


- Millions of alveoli
- Gases must be in
that allows a greater
solution to diffuse
surface area, essential into alveoli
...


!

!

Mechanisms of Breathing
- The lungs are ventilated by muscular movements of the wall of the thoracic cavity, diaphragm

-

-

and the abdominal wall
...
Air
pressure is hence lower than the outside and air rushes in to equalise the pressure, known as
INSPIRATION
...

The lungs are enclosed in the PLEURAL CAVITY
...

Pleural cavity is air-tight and has a lower atmospheric pressure than in the lungs
...
It also prevents the lungs collapsing
...

The concentration of oxygen int he blood is lower than that in the alveoli; and the concentration
of carbon dioxide in blood is higher than that in the alveoli
...

This concentration difference is maintained by ventilation of the lungs, which expels carbon
dioxide and replenishes oxygen
...
The red blood cells have to squeeze through, causing them to flatten out
...


Control of Breathing
- The body has two methods of regulating breathing:
1
...
This fluid is determined by carbon dioxide in the
blood
...
Sensors in the aorta and carotid arteries that
monitor carbon dioxide concentrations, as well as blood pH
...

2
...


Excretory System
- EXCRETION is the removal from the body of the waste products of metabolic activities
...


- KIDNEY keeps body’s internal environment constant by:

-

• Removal of nitrogenous wastes (e
...
urea)
• Maintaining an ion and water balance in the blood plasma
• Divided into two main regions: OUTER CORTEX and MEDULLA
RENAL ARTERY carries blood to the kidneys directly from the heart via the aorta
...

URETER transports urine from the kidney to the bladder
...

URETHRA transports and excretes urine from the bladder to outside of the organism
...
Inside the kidney the
artery divides into capillaries with little loss in blood pressure
...

The Bowman’s Capsule is the beginning of a 3 cm tube called a NEPHRON
...

Blood enters the glomerulus under high pressure; this pressure is increased because the efferent
arteriole is slightly smaller than the afferent arteriole
...
This liquid is called GLOMERULAR FILTRATE
...

About 7
...

Glomerular filtrate flows out of Bowman’s Capsule into the tubular part of each nephron, known
as the PROXIMAL CONVOLUTED TUBE, LOOP OF HENLE, and DISTAL
CONVOLUTED TUBE
...

Sodium ions are actively absorbed in the proximal tubule creating an ionic imbalance that results
in the passive movement of chloride ions by diffusion
...

Distal convoluted tube is responsible for reabsorption of other ions and the secretion of some
substances
...

Removal of useful substances from the filtrate produces URINE
...
Urine drains out
of the nephrons in to COLLECTING DUCTS, and into the ureters and out of the body
...

- The cells of every organism require a STABLE ENVIRONMENT in order to function at an

-

-

optimal level
...

The EXTERNAL ENVIRONMENT of an organism is made up of water, air and soil
...

The control of body temperature, water balance, glucose level and oxygen level are all under
HOMEOSTATIC CONTROL
...

The response to any given stimulus can be represented in a simple diagram called a
STIMULUS-RESPONSE MODEL
...

The CNS will send messages via INTER-NEURONES throughout the CNS to elicit an
appropriate response, either directly via a MOTOR NERVE or indirectly via hormones released
into the bloodstream
...

Homeostasis is important for enzyme activity and cell size
...

The self regulating mechanism is achieved by negative feedback
...

THERMOREGULATION is an example of a negative feedback loop
...
Rare in biology because it tends to produce harmful, unstable conditions
...
The
contractions trigger a positive feedback reaction
...

Homeostasis involves:
• Skin: thermoregulation
• Liver: blood sugar, amino acids
• Kidneys: removal of waste and osmoregulation
• Lungs: oxygen and carbon dioxide

- When the body is too hot, sweat glands pour liquid onto the skin, where it evaporates and cools

-

the body
...

In cold weather, sweat glands cease to work and arterioles contract (undergo
VASOCONSTRICTION)
...

Mammals need to ensure the volume of blood plasma and concentration of dissolved substances
in the blood and tissue fluid stay relatively constant
...
This varies
the amount of ANTIDIURETIC HORMONE (ADH) released into the bloodstream
...

The kidneys respond to a change in ADH concentration by adjusting the volume and
concentration of the urine
...

- Its target cells are the ENDOTHELIAL CELLS of the collecting ducts of the kidney nephrons
...
ADH causes these water
channels to open
...

- Two parents are needed in SEXUAL REPRODUCTION, and the offspring produced are

-

-

-

-

-

-

-

-

genetically different to the parents
...

Only one parent is needed in ASEXUAL REPRODUCTION, and the offspring produced are
genetically identical to the parent, e
...
reproduction in bacteria, production of spores by fungi,
and the formation of tubers in potatoes and bulbs in daffodils
...

Reproduction involves a series of events called the REPRODUCTIVE PROCESS and these
processes are complex, involving structural, functional and behavioural characteristics
...

When environmental factors are favourable, asexual reproduction is employed to exploit suitable
conditions for survival such as an abundant food supply, adequate shelter, favourable climate,
disease and an optimum pH
...

When food sources have been depleted, the climate becomes hostile, or individual survival is
jeopardised by some other adverse change in living conditions, these organisms switch to sexual
reproduction
...
Introduces variation into a population
2
...
A disease is less likely to affect all the individuals in a population
These are some of the disadvantages of sexual reproduction:
1
...
Not possible for an isolated individual
The advantages of asexual reproduction include:
1
...
Can exploit a suitable habitat quickly
The disadvantages of asexual reproduction include:
1
...
The species may only be suited to one habitat
3
...
g
...


- PARTHENOGENESIS is when an individual produces eggs that already have the full genetic
number (diploid) rather than the usual haploid number of a sex cell
...


Plant Asexual Reproduction
- VEGETATIVE PROPAGATION is a type of asexual reproduction in which a plant gives rise

-

-

-

-

to new plant individuals, without production of seeds or spores
...
This results in genetically identical plants so that
successful varieties are maintained
...

For example, a small axillary or terminal protuberance on a plant, containing rudimentary foliage
(leaf bud), the rudimentary inflorescence (flower bud) or both (mixed bud)
...
g
...
New stems and roots
can develop above stem, on the parent stem, from buds along the nodes of the parent
...

FRAGMENTATION is a process in which multi-cellular organisms break apart into smaller
parts, when they are mature
...
g
...
Taking a cutting from a plant is a form of
fragmentation
...

The blobs contain cells or spores that can eventually develop into new mould individuals
...
In spore formation, reproductive cells containing a nucleus
and cytoplasm produced by mitosis so it is genetically identical to the parent (e
...
protists and
fungi)
...

Some plants naturally produce side branches with plantlets on them
...

Other plants, such as strawberries, produce RUNNERS with plantlets on them
...


- GRAFTING involves joining structures from two or more plants (way of producing new

-

varieties, can select favourable characteristics)
...

CUTTING is when sections of a parent plant, which are removed and grown as new individual
plants
...


Plant Sexual Reproduction
- Flowers are important in the sexual reproduction of plants
...
These must meet for reproduction to begin: a process called POLLINATION
...
It is collectively called the calyx
...

The PETAL may be brightly coloured to attract insects
...

The STAMEN is the male part of the flower, comprising an anther attached to a filament
...

The ANTHER produces the male sex cells (POLLEN)
...
It is the
receptive part of the carpel and pollen grains will germinate only if they land here
...
It is at the base of the
carpel
...

The PEDICEL is a small stalk or stalk-like part bearing a single flower in an inflorescence
...
It sometimes forms the succulent tissue of
the fruit
...

- The BRACT is a specialised leaf or leaf-like part, usually situated at the base of a flower or
-

inflorescence
...

The female parts of the flower together are called the CARPEL
...


-

Pollination
- Before fertilisation can occur, pollen must first be transferred from the anthers to the stigma, and

-

-

this is known as POLLINATION
...
Usually one plant receives pollen from
other plants in a process known as cross-pollination
...
This
doesn’t allow for genetic change, but ensures the development of fertile seeds
...

It is the transfer of pollen grains from the anther to the stigma of the same flower or another
flower born on the same plant
...

Bother anthers and stigmas mature at the same time
...

Produces homozygous offsprings
...

CROSS-POLLINATION involves the transfer of pollen from one plant to another and usually
involves an active vector (e
...
insects such as bees) or a transporting medium (e
...
wind)
...

An external agent (wind, water, insects, etc
...


-

Anthers and stigmas mature at different times
...

Produces heterozygous offsprings
...


Types of Flowers
- Flowers with brightly-coloured petals are usually INSECT-POLLINATED flowers
...
Insects carry pollen from one flower to
another
...

Have a special arrangement to attract insects, i
...
mimicry and pseudo-copulation
...

The flower is usually scented and with nectar to attract insects
...

The pollen grains are sticky or spiky so that they can stick to insects well
...

The stigma is inside the flower, sticky and the pollen grains stick to it when an insect brushes
past
...
These are also known as ANEMOPHILOUS
FLOWERS
...

The petals are small, often dull green or brown - no need to attract insects
...

Has a large amount of pollen grains
...

Pollen grains are smooth and light and are easily carried by the wind without clumping together
...

The stigma is outside the flower and is feathery to form a network to catch drifting pollen grains
...

It grows through the style until it reaches an ovule inside the ovary
...
This process is
called FERTILISATION
...
To produce the embryo
2
...


- After fertilisation the female parts of the flower develop into a fruit:

-

1
...

2
...

Once the fruit has developed the other parts of the flower that aren’t required shrivel and drop
off
...


Seeds and Germination
- During the development of the seed, its cells become specialised and group together to form the

-

-

shoot, root and the first leaves of the embryo/young plant
...

The SEED is an entire reproductive unit, it keeps the embryonic plant in a dormancy state
...

The embryo stops growing and remains in a dormant state until the seed germinates
...
PLUMULE that becomes the main stem
...
COTYLEDON is the seed leaf, which is the beginning of the leaves
...
RADICLE becomes the root
...
ENDOSPERM that contains a supply of stored food for the embryo
...
TESTA is the outer layer of the seed that is usually hard and thick, which protects the
embryo and stops it from drying out
...
HILIUM is a scar on the testa where the seed is attached to the ovary
...
ROOT CAP (not present in dicot seeds)
...
It

-

ensures that a plant’s seeds are distributed across a wider range
...

The agents of seed dispersal include:
1
...
g
...

2
...

3
...

4
...
These
seeds tend to be light in weight with a large surface area
...
Water: many seeds readily dispersed, even when the lack special buoyancy mechanisms
...
They are then carried away,
and deposited in the silt or the stream
...
Animals: catch on fur (dry seeds) using hooks, spikes or sticky coating; or through
consumption (fleshy fruits), the animal eats the fruit and the seed comes out in the faeces
unharmed by the digestive system, or dropped during transportation
...
Other mechanisms: explosive discharge or sharking from pods or capsules (e
...
poppy,
legumes)
...

Most seeds remain inactive/dormant until the right conditions come along
...

Three main factors are needed for successful germination:
1
...

2
...

3
...

Germinating seeds use their food stores until the seedlings can produce their own food by
photosynthesis
...


- As the seed germinates, the root and shoot appear (their growth depends on moisture gravity and
-

light)
...


Fruit
- FRUIT are mature ripened ovaries
...

- Pericarp has three regions: OUTER EXOCARP, CENTRAL MESOCARP and INNER
ENDOCARP
...

- The two main fruits are:
1
...
Examples
include peas and beans
...
FLESHY FRUITS that are usually dispersed by animals
...

- Fruits only occur in angiosperms (part of evolution)
...

This process involves a haploid multicellular generation/plant structure called a
GAMETOPHYTE, which is formed from the spore and give rise to the haploid gametes
...

The multicellular diploid plant structure is called the SPOROPHYTE, which produces spores
through meiotic (asexual) division
...

DIPLOID means having two sets of chromosomes and is indicated by ‘2n’
...

- The fertilised cell grows into a seed and then a plant
- Gymnosperms: cones, wind, no water needed, can use fire
- Angiosperms: gametophyte part includes pollen and ovules, sporophyte is rest of flower
- Pollination by bees, butterflies, hummingbirds

Diversity in Reproductive Strategies
- In alternating sexual and asexual cycles, organisms such as coral can reproduce sexually and

-

-

-

asexually
...
This happens when the parent polyp reaches a certain size and divides
...
They release
massive numbers of eggs and sperm into the water to distribute their offspring over a broad area
...

Large numbers of planulae are produced to compensate for the many hazards - such as predators
and water currents
...
These include amphibians, fish
(pisces), birds (aves), reptiles and mammals
...

In INTERNAL FERTILISATION AND EXTERNAL DEVELOPMENT, organisms
reproduce by having a courtship ritual, the fertilisation is internal, and the eggs are laid and
develop externally
...

In INTERNAL FERTILISATION AND DEVELOPMENT, fertilisation and development
occurs inside the female for a long period of development
...

EXTERNAL FERTILISATION is a strategy of fertilisation in which a sperm cell unites with
an egg cell in the open
...

No copulation occurs
...

Many female gametes are produce
...

INTERNAL FERTILISATION is the union of an egg cell with a sperm during sexual
reproduction inside the body of a parent
...

Copulation occurs (e
...
sexual intercourse of male and female with transfer of gametes)
...

Few female gametes are produced; this saves body materials
...

HERMAPHRODITISM is where the sperm and eggs are produced in the same individual
...
Examples
include worms and snails
...
They have the same number of chromosomes and DNA
instructions
...


- CYTOKINESIS is the process in which the cell membrane pinches inwards so that a new
-

-

membrane is formed, dividing the cell into two
...

GAMETES contain one set of chromosomes (haploid) and a total of 23 chromosomes
...

This process results in the chromosome number being halved, so instead of pairs of
chromosomes in each resulting cell, there is only one chromosome from each pair
...

The ‘crossing over’ of genetic information between each pair of chromosomes is a source of
variation in a species
...


- VARIATION within a species can provide some individuals with an increased chance of
-

-

survival
...

In humans, FERTILISATION occurs when a haploid gamete from each parent fuse together to
form a diploid zygote
...
This is another source of genetic variation that can give sexually reproducing organisms
an increased chance of survival
...
Each pair of chromosomes will consist of a chromosome from each parent
...


Gametogenesis
- GAMETOGENESIS is the process by which diploid oocytes or spermatocytes undergo meiosis
to form mature haploid gametes (sperm and ova)
...

- OVA are haploid and have only one copy of each gene
...

The process begins during foetal development, when a large number of oocytes are formed by
mitosis
...

At puberty, some follicles continue to develop each month in response to FSH secretion
...

The cell with less cytoplasm is a POLAR BODY, which degenerates, while the larger cell forms
a secondary oocyte
...

The second meiotic division will produce an ovum and a second polar body
...

OVULATION is the release of a secondary oocyte from the ovaries
...

The first stage of sperm production requires the division of germline epithelium by mitosis
...

This is followed by two meiotic divisions that result in four haploid daughter cells (spermatids)
...


- The head of a sperm cell contains the haploid nucleus, which is covered by the ACROSOME, a

-

structure enclosed by a membrane that contains hydrolytic enzyme to break through the egg cell
membrane at fertilisation
...

The FLAGELLUM is a bundle of contractile rods that give the sperm a means of locomotion
...

• Both processes involve mitosis, growth and meiosis
...


-

-

The fluids provide the sperm cells with nutrients (fructose) for respiration
...

PROSTATE GLAND secretes fluid that helps activate sperm during ejaculation
...

VAS DEFERENS moves sperm from epididymis to urethra using muscular movements
...
A ring of muscle ensures that the urine and semen do not get mixed up
...

EPIDIDYMIS stores sperm while they mature and develop the ability to swim, site at which
testicular fluids are removed, concentrating the sperm
...

SCROTUM contains and supports the testes and keeps them cooler than the rest of the body
(necessary for sperm production)
...


- FORESKIN protects the glans penis
...


Female Reproductive System
- FALLOPIAN TUBE serves as a passage through which eggs pass on their way from the ovaries

-

-

to the uterus
...

OVARY produce eggs (ova) and produce the female sex hormones oestrogen and progesterone
...
It is a muscular bag with a soft lining, and is where a baby
develops until birth
...
It is a ring of muscle at the lower end of the uterus and keeps the baby in place until birth
...

VULVA consists of labia major and labia minor, which are protective folds
...
Bartholin’s glands secrete lubricating mucus
into the opening of the vagina during sexual excitement
...


Menstrual Cycle
- Starting at puberty, the female reproductive system undergoes a regular sequence of events,

-

-

-

-

-

-

repeated monthly, called the MENSTRUAL CYCLE
...

During one menstrual cycle an ovum is released from one ovary and the lining of the uterus is
renewed
...
These events are controlled by hormones from the
pituitary gland and the ovaries
...

When the discharge stops, one of the ovaries is stimulated by the secretion of FOLLICLESTIMULATING HORMONE (FSH) from the pituitary gland
...

The ovary responds by developing one or more follicles
...

The main function of OESTROGEN is to stimulate the growth of a new uterine lining
...

It stops FSH being produced (so only one egg matures in a cycle)
...

The rising level of oestrogen in the blood acts as a feedback mechanism: it causes the pituitary to
stop producing FSH and start producing another hormone which brings about ovulation, known
as LUTEINISING HORMONE
...
Immediately after ovulation a woman is
said to be fertile and can conceive
...

This acts as a temporary endocrine organ and produces the hormone progesterone
...

Meanwhile, the ovum has been sucked into the fallopian tube and is moved toward the uterus to
be fertilised
...

Death of the ovum is soon followed by a gradual reduction of the corpus luteum and a reduction
in the amount of progesterone produced
...
The cycle repeats itself
...

During OVULATION, there is a surge in luteinising hormone that causes ovulation and a
rupturing follicle creates a corpus luteum
...

A PHEROMONE is a chemical an animal produces that changes the behaviour of another
animal of the same species (including insects)
...

Pheromones are ECTOHORMONES, which means they act outside of the body of the
individual that is secreting them and impact a behaviour on another individual
...


- TESTOSTERONE causes the development of male primary sexual characteristics (male
-

-

genitalia) in the embryo at about 6 weeks
...

In adults, testosterone plays a role in maintaining the sex drive and production of sperm
...

A large number of sperm are necessary because many fail to complete the long journey due to:
1
...
g
...

2
...

3
...

4
...

5
...

Sperm swim through the cervix into the uterus and up the fallopian tubes, which is aided by
muscular contractions of the uterus during copulation
...

The sperm (only head) must penetrate a membrane surrounding the ovum
...


- A fertilised ovum is called a ZYGOTE
...

By the time it reaches the uterus it is around 100 cells
...

Unequal divisions beyond this stage cause a fluid-filled cavity to form in the middle - this makes
a BLASTOCYST (day 7)
...

IMPLANTATION is when the blastocyst reaches the uterus and embeds itself in the
endometrium
...

Within three weeks of implantation, food and oxygen are absorbed within the placenta
...

The placenta is a temporary endocrine organ, producing large amounts of progesterone and
oestrogen
...

The progesterone ensures that the uterus grows at the same rate as the baby and the breasts are
ready to produce milk as soon as the baby is born
...

The embryo’s heart pumps blood through blood vessels in the umbilical cord into the placenta
...

There is no mixing between the mother’s blood and that of the embryo
...
The amnion acts
as a shock absorber, cushioning the baby and ensuring the baby develops in a constant
environment
...

As this is often difficult to determine, age is determined from the mother’s last period known as
the MENSTRUAL AGE
...

It has a bulge at one end that will develop into the head, brain, eyes and ears that are beginning to
develop
...
The embryo has a long tail,
-

-

small lumps on its sides that are developing into arms and legs
...

It has a face and limbs with fingers and toes
...

At Week 20, the foetus is about 25 cm long
...
The sex organs are developed
...
It has soft downy hair and
eyelashes
...

It is covered with VERNIX that stops the skin becoming water logged with amniotic fluid
...

It is legally viable from week 28
...

Week 40: the pregnancy is now at TERM and the baby is ready to be born
...
5 kg and is about 50 cm long
...

It attaches the foetus to the uterine wall
...

Allows the foetus to transfer waste products to the mother’s blood
...

Maternal blood supplies the foetus with oxygen, glucose, lipids, water, minerals, vitamins,
antibodies, hormones, amino acids
...

Nutrients and oxygen diffuse from the maternal blood into the foetal blood
...

The umbilical cord connects the foetus to the placenta and maternal blood pools via open ended
arterioles into intervillous spaces (LACUNAE)
...

Nutrients, oxygen and antibodies will be taken up by the foetus, while carbon dioxide and waste
products will be removed
...

The placenta takes over the hormonal role of the ovary (around 12 weeks)
...


- Progesterone maintains the endometrium, as well as reduces uterine contractions and maternal
-

immune response (no antibodies against foetus)
...


Foetal Circulation
- FOETAL CIRCULATION is different to normal human circulation as exchange does not occur

-

-

-

-

in the lungs and nutrients are not consumed by eating
...
It allows blood to move from the right
atrium to the left atrium only, bypassing the lungs and allows the oxygenated blood from the
placenta to be delivered to the body
...
This
duct acts to direct blood away from the lungs and into the systemic circulation
...

The DUCTUS VENOSUS receives blood from the umbilical vein and directs it to the posterior
and inferior vena cava
...

UMBILICAL VEIN joins to vena cava
...

UMBILICAL ARTERY carries deoxygenated blood with foetal waste from the foetus to the
placenta
...


Effects of Drugs on the Foetus
- The effects of drugs on growing foetuses has been studied widely
...

Thalidomide was widely prescribed to relieve morning sickness in pregnant women
...

The birth of these children soon became known as ‘history’s greatest medical disaster
...

The effects of drugs on the foetus depends on the baby’s stage of development and how much of
the drug is ingested
...

ALCOHOL causes damage to the CNS, can cause birth defects, increases the risk of
miscarriage, can cause poor attention and hyperactivity later in childhood
...

CANNABIS: hard to know the extent of the effects because it is usually mixed with tobacco and
alcohol, crosses the placenta, may increase stress on baby and impulsiveness in children
...

HEROIN, MORPHINE (OPIATES): cross the placenta, foetus can become addicted, birth
defects, respiratory depression, problems, baby can be irritable or drowsy
...
All drugs pass through the
placenta
...

It is typical for mammals, but also occurs for some non-mammals (scorpions, some sharks,
worms and lizards)
...

During the months before birth, the uterus walls develop a thick layer of muscle
...

A few days before birth the baby turns in the uterus until its head points towards the cervix
...

During the second stage of birth, contractions are strong and close together
...

During the third stage of birth, further contractions of the uterus push the placenta and umbilical
cord (after birth) from the body
...

- After approximately 9 months, the foetus is fully grown and takes up all the available space in
-

the uterus, stretching the uterus walls
...

The pituitary in the brain secretes oxytocin which inhibits progesterone that was inhibiting
uterine contractions
...

The contraction of the uterine muscles causes further stretching which triggers more oxytocin to
be released (positive feedback)
...


Twins
- MONOZYGOTIC TWINS (identical twins) develop when an egg fertilised by a sperm

-

completely splits into two eggs soon after fertilisation (an incomplete split results in conjoined
twins)
...

DIZYGOTIC TWINS (non-identical twins) develop when two eggs are fertilised by two
different sperm
...

Each embryo has its own placenta
...

The majority of babies who experience NAS show signs within 24-72 hours after birth
...

ILLEGAL OPIATES, such as heroin and opium, taken during pregnancy can result in NAS
...

Symptoms include excessive crying, fever, irritability, seizures, slow weight gain, vomiting and
even death
...

If taken in the third trimester there is no chance of malformation but effects on the baby can
include respiratory depression
...

The majority of people seeking assisted conception technologies are infertile
...

It affects 15% of Australian couples of reproductive age
...

The causes of infertility include endometriosis, tubal damage/obstruction, cervical mucous,
ovulatory failure, poor sperm quality or disease
...

There are also ongoing debates about the ethical, moral and legal dimensions of reproductive
technology
...

IN-VITRO FERTILISATION (IVF) means literally fertilisation in a glass
...
After fertilisation occurs, the embryo or
embryos are transferred to the uterus
...
There are several types of IVF, depending on whether the woman
or man is the cause of the infertility and how severe it
...

ZYGOTE INTRA-FALLOPIAN TRANSFER (ZIFT) is where the egg and sperm are fertilised
outside the body (as with IVF) and the embryo (zygote) is transferred to the fallopian tubes
...

The embryo is then used in an IVF or ZIFT procedure
...
Surrogacy is often
separated into commercial (where the bearer of the child is paid for her services) and altruistic
(where the bearer receives no payment)
...

IVF, GIFT, and ZIFT usually involve chemically stimulating the ovaries to produce more eggs
which are extracted by a procedure called a laparoscopy or needle through the uterus
...


Ethics of Reproductive Technologies
Arguments for:
1
...

2
...

3
...

Arguments against:
1
...
e
...

2
...

3
...

4
...


Contraception
- INTRAUTERINE DEVICE (IUD) is a T-shaped device with a copper wire around it
...

It causes changes in the lining of the uterus, prevents the sperm from fertilising the egg,
decreases the ability of the sperm to penetrate the cervical mucus
...
Long-acting contraceptive (can be left in place for up to five years)
...
No daily contraceptive routine required; device provides five years of contraception
...
Does not contain oestrogen
...
Does not interfere with intercourse
...
May reduce the risk of endometrial cancer
...
May be suitable for women who are breastfeeding
...
Possible side effects include irregular bleeding or spotting in the first months after
insertion
...
Perforation of the uterus may occur at the time of insertion but this is rare
...
May increase menstrual bleeding or menstrual cramping
...
May be expelled from the uterus (happens in 2-10% of IUD users)
...
Does not protect against STIs
...

- The condom fits over the erect penis, acts as a physical barrier preventing direct genital contact
and the exchange of genital fluids, so the sperm does not enter the uterus and fertilise the egg
...

- Advantages include:
1
...

2
...

3
...

4
...

5
...

6
...

- Disadvantages include:
1
...

2
...

3
...

4
...

5
...

6
...

7
...


BIOLOGY TERM 3 NOTES: GENETICS
Meiosis
- MEIOSIS is the type of cell division by which gametes are produced
...

- Comprises of two successive nuclear divisions with only one round of DNA replication
...

Meiosis reduces the chromosome number such that each daughter cell has only one of each pair/
kind of chromosome
...
The diploid number of chromosomes
...
A combination of traits that differs from that of either parent
...

Following DNA replication, each chromosome is duplicated
...

During Meiosis II, the centromeres divide and the sister chromatids separate, becoming daughter
chromosomes that move into the daughter nuclei
...

Prior to Meiosis I, DNA replication occurs
...

No replication of DNA occurs between Meiosis I and Meiosis II
...
Synapsis is significant because it leads to a reduction of
the chromosome number
...
Daughter cells are haploid, but
chromosomes are still in duplicated condition
...
The completely haploid daughter cells mature into
gametes
...


- The period of time between Meiosis I and Meiosis II is called INTERKINESIS
...

PROPHASE I is where each chromosome duplicates and remains closely associated
...
Crossing-over can occur during the latter part of this stage
...

ANAPHASE I is where the homologous pairs separate with sister chromatids remaining
together
...


- PROPHASE II is where the DNA does not replicate
...

- ANAPHASE II is where the centromeres divide and sister chromatids migrate separately to each
-

pole
...
Four haploid daughter cells are
obtained
...

Offspring with genotypes unlike either parent are known as recombinants
...


- There are three sources of genetic recombination:

-

1
...

2
...

3
...

During Meiosis I, duplicated homologous chromosomes undergo synapsis
...


Comparison of Mitosis and Meiosis
Mitosis

Meiosis

Requires one division
...


Two diploid daughter cells result from mitosis
...


Daughter cells from mitosis are genetically identical
to parental cells
...


Mitosis occurs in all somatic cells for growth and
repair
...


Prophase - has no such pairing
...


Metaphase - chromosomes align at metaphase plate
...


Anaphase - sister chromatids separate
...


Telophase - diploid cells
...


Genes and Variation
- All living things (with the exception of some viruses) contain deoxyribonucleic acid (DNA)
...
A gene

-

is a section of a DNA molecule
...

Features such as scars and skills are called ACQUIRED CHARACTERISTICS
...

Other characteristics that have no or few intermediate forms show DISCONTINUOUS
VARIATION, such as tongue rolling, cleft chin or dimples
...

DNA is the main component of chromosomes, which are found in the nucleus of cells
...
Heritable factors are things
like ear lobe attachment, eye colour or skin colour
...

For example, the gene for eye colour can occur as either light or dark (each form is called an
allele)
...

A CHROMOSOME is a structure found in the nucleus of cells
...

There is also 2 of each type forming what is called HOMOLOGOUS PAIRS, meaning that
there is a total of 46 chromosomes in human cells
...

Since organisms have two genes for each characteristic, it is possible for them to either be the
same or different allele
...

HETEROZYGOUS has two different alleles of a gene
...
g
...

PHENOTYPE is the observable characteristic that a person has (e
...
can roll tongue)
...

A RECESSIVE ALLELE is an allele that only has an effect on the phenotype when present in
the homozygous state
...

LOCUS is the particular position on homologous chromosomes of a gene
...

A TEST CROSS is testing a suspected heterozygote by crossing it with a known homozygous
recessive
...

- DNA is a large molecule, made up of many chemical building blocks called nucleotides
...

- The ribbon-like strands consist of sugar-phosphate backbone and the horizontal steps are base
pairs
...


- All nucleotides contain a phosphate group, a deoxyribose sugar and a nitrogen-containing base
...
ADENINE (A) and GUANINE (G) are PURINE bases as they have two rings in their
molecular structure
...
THYMINE (T) and CYTOSINE (C) and URACIL (U) are PYRIMIDINE bases as they
only have one ring in their molecular structure
...

In eukaryotic cells, DNA is packed as chromosomes in the nucleus
...

Eukaryotic DNA is associated with proteins called HISTONES
...

In prokaryotic cells, DNA is loose in the cytoplasm - there are no histones or chromosomes
...
At one end of each strand there is a phosphate group attached to
the carbon atom number 5 of the deoxyribose (this indicates the 5’ terminal) and at the other end
of each strand is a hydroxyl group attached to the carbon atom number 3 of the deoxyribose
(indicates the 3’ terminal)
...

Adjacent nucleotides are attached together via a bond between the phosphate group of one
nucleotide and the carbon atom number 3 of the deoxyribose of the other nucleotide
...

A purine will ink with a pyrimidine
...


DNA Replication
- The DNA molecule is passed on from one cell to another in mitosis and meiosis and from parents

-

to offspring in the union of gametes at fertilisation
...

DNA replication involves synthesising new DNA during interphase
...

• DNA replication is semi-conservative because each daughter DNA molecule consists of
one old and one newly synthesised strand
...

• As the old strands unzip (separate from each other when the hydrogen bonds are broken), a
new strand is synthesised against each old strand
...


- DNA replication is extremely accurate
...

-

Where this does occur, proof-reading and repair enzymes correct the error
...
Enzymes unwind the DNA molecule to expose the two original strands
...
DNA polymerase enzyme uses the two original strands as templates to make
complementary strands
...
The two resulting double-helix molecules coil to form two sister chromatids
...

- It contains thousands of sections called genes or CISTRONS
...

- All polypeptides are made from amino acids, so the sequence of bases in a gene must code for

-

amino acids
...

The existence of a TRIPLET CODE was confirmed by experiments by Francis Crick in 1961
...

When a polypeptide is required, the triplet code of its gene is converted into a molecule of
MESSENGER RNA (mRNA)
...


- During transcription, the mRNA is built up by complementary base pairing, using the DNA as a
-

template
...

The three base codons are the instructions for the cell to make proteins from the amino acids
...

Once a molecule of mRNA has been transcribed, it moves out of the nucleus via a nuclear pore
...

In the cytoplasm, amino acids become attached to TRANSFER RNA (tRNA) molecules
...

Each tRNA molecule has a sequence of three bases called an ANTICODON
...


- tRNA molecules attach to the ribosome, and their anticodons pair up with the appropriate codons
-

on the mRNA
...

The ribosome moves along the mRNA, and amino acids continue to join together until all the
codons have been translated and the polypeptide is complete
...

The main types of mutation include substitution, deletion, translocation and insertion
...


- The consequences of mutation can be:
1
...
For example, GGC to GGU has no effect because it
still makes glycine in either case
...
MIS-SENSE MUTATION: substitution of a nucleotide causes a new amino acid
...

Dwarfism (achondroplasia): GGA (Gly) to AGA (Arg) substitution
...

3
...

Muscular dystrophy is caused by frameshift mutations in the dystrophin gene (muscle
protein)
...

4
...

PKU (phenylketonuria): UGC (Cys) to UGA (stop)
...
Fortunately, all newborns are screened for PKU, which is treatable by avoiding all
phenylalanine-containing foods
...

- MUTAGENS, such as x-rays, UV rays (sunlight), chemicals and tobacco, can cause mutations
...

They can be represented by two capital letters superscript to the letter representing the gene
...


- CO-DOMINANCE is when both alleles are expressed in the phenotype of the heterozygote
-

offspring
...


- Some genes have multiple alleles (more than two), but only two can be present in an individual
...


- A and B are co-dominant and O is recessive to both
...
e
...

- For each characteristic, an organism inherits two alleles, one from each parent
...
SEGREGATION: In diploid organisms, chromosome pairs (and their alleles) are
separated into individual gametes (eggs or sperm) to transmit genetic information to
offspring
...
DOMINANCE: A dominant allele completely masks the effects of a recessive allele
...

3
...

- To determine whether an organism showing the dominant characteristic of a trait is homozygous
or heterozygous, a TEST CROSS can be performed
...

- If any of the offspring show the homozygous recessive trait in the phenotype, the parent must
have been heterozygous
...


- The roman numerals indicate the generation each person belongs to
...

- A MONOHYBRID CROSS is the study between organisms that differ in a single given trait
...

- The X chromosome is larger and contains about 2000 genes, whereas the Y chromosome

-

-

contains fewer than 100
...

Males (XY) are the HETEROGAMETIC sex
...

X-linked diseases include haemophilia, muscular dystrophy, red-green colour blindness
...

HAEMOPHILIA is an X-linked, recessive condition where the blood does not clot normally,
resulting in excessive bleeding
...

The ratio of a dihybrid cross is thus 9:3:3:1 in the F2 generation when there is heterozygous
organisms with two genes that show full dominance
...


Genetic Interactions
- Genes interact with each other and with their environment
...

In addition, the level of interaction will vary between organisms and will therefore affect
variation within a species
...

The distribution of dark and light fur colour in Siamese cats (known as point colouration) is a
result of the effect of the environment of the functioning of a mutated enzyme, tyrosinase,
involved in melanin production
...

The enzyme is active at lower temperatures, resulting in darker fur at the extremities (i
...
face
and feet)
...

Most examples involve more than two co-dominant genes
...

An example is human skin colour, which depends on the quantity of the pigment melanin
...

Genes that are closely located on the same chromosome tend to be inherited together and are
known as a LINKAGE GROUP
...

In crosses where linkage is a contributing factor, a large proportion of the offspring are of the
parental type
...

All the alleles on one chromosome form a linkage group
...

The occurrence of crossing-over can help determine the sequence of genes on a chromosome
...

Dominance and recessive alleles are caused by genes code for polypeptides, polypeptides are
processed into proteins and these function as enzymes, structural proteins and hormones
...
The changes that take place occur slowly, over millions of years,
and represent different species gradually developing in different and changing environments
...
5 billion to 6 billion years old
...

99% of all species that ever lived are now extinct
...
Physical traits and behaviours enable organisms to survive and reproduce (fitness)
...
Fitness results from adaptations
...
Darwin reasoned that adaptations result from natural selection that results in evolution
...

The creation of the fossil record substantiates the process of biological evolution
...

FOSSILS are the remains and impressions of ancient life, both plant and animal
...
The skeletons of extinct races of man are also considered fossils
...
Two conditions are almost always present:
1
...

Organisms such as jellyfish or worms leave little record
...
QUICK BURIAL of the dead organism, so that it is protected against weathering,
bacterial action and scavengers
...

Fossils form when organism is buried in sediment quickly, calcium in bone or other hard tissue
must mineralise and surrounding sediment must harden to form rock
...


- A fossil forms in the following steps:
1
...
BURIAL AND PRESERVATION: the organism can only become a fossil if it is covered
over by sediments quickly
...
The hard body parts such as bones are all that remains
...

3
...
Hard body parts such as bone and teeth are replaced by new
minerals such as calcite or quartz or pyrite, known as PETRIFICATION
...

4
...

5
...
The best places to find fossils is where
the rocks have recently been lifted up or exposed (cliffs, quarries or road cuttings)
...

Petrification is the conversion to stone by PERMINERALISATION, the filling of pores by
mineral matter dissolved in groundwater
...
Every detail of the surface is preserved
...

CARBONATION or DISTILLATION is the loss of volatile elements of the organism and the
concentration of carbon which outlines the original form of the organism
...
A thin mould, such as a leaf, is called an
IMPRINT
...


- COPROLITE is fossilised excrement of animals and may reveal the feeding habits of ancient
-

-

animals
...
They are very useful in determining how an organism lived,
moved and fed
...
MARINE SEDIMENTS: the most important environment for preservation
...
FRESHWATER SEDIMENTS: beds of lakes, floodplains, deltas, quicksand
...
BOGS: swampy ground covered with vegetation often mires many animals
...
TUNDRA: the frigid frozen soils of the northern continents preserve many Pleistocene
mammals
...

- RELATIVE AGE DETERMINATION is where one compares the age of fossils by looking at

-

-

-

-

their position within the stratigraphic column
...

ABSOLUTE AGE DETERMINATION is where the calculated age of a fossil is achieved
using radioisotope dating
...
After death these compounds then breakdown by
radioactive decay
...
Carbon-14 is radioactive and
is present in the atmosphere in measurable amounts (for this type of dating) and in constant
proportions
...
This produces plant material that is radioactive, e
...
glucose,
protein or fats
...
When the animal or plant dies, its
body contains carbon-14
...

Carbon-14 breaks down by half every 5558 years, but normal carbon does not break down
...

Radiocarbon dating can be used to estimate fossils ages up to about 50,000 years old
...

If a fossil read 0
...

Carbon has a very short half life so to date older fossils we use one of the isotopes listed below
...

By studying the anatomy and physiology of various organisms, likeness between different
species becomes apparent
...

For example, all vertebrate embryos have a tail, a two chambered heart and rudimentary gills in
the throat region, suggesting a common ancestor
...

PHYLOGENY is the evolutionary branching process and the history of an organism’s lineage as
they change through time
...
This implies that the homologous structures are evidence for similar genes which
have been inherited from a common ancestor, such as a pentadactyl limb
...

- Scientists believe that organisms with vestigial structures are related to those that have the
-

structure developed or functional
...
Whales have vestigial legs
relating them to mammals
...


- BIOCHEMICAL SIMILARITIES exist between living organisms
...
Also, organisms share their DNA or
RNA structure
...

DNA HYBRIDISATION is used to determine how genetically similar two organisms are
...

This hybrid then undergoes heat treatment in order to separate it
...
The greater the termal stability, the closer
the organisms are
...
These structures have the same
-

function in different organisms with different origins
...

BIOGEOGRAPHY is the study of plant and animal species’ distribution
...

Its significance is that different forms evolved from ancestral populations that RADIATED out
from a central population to new environments
...

If a barrier were to form, e
...
a mountain range or desert, then the species either side of the
barrier would become geographically isolated and could not interbreed with the other population
...
The alleles in the offspring are a sample of those in the parents, and
chance has a role in determining whether a given individual survives and reproduces
...

For example, the population of Finches on the Galapagos Islands demonstrates macroevolution
...

It is believed that these species originated from an ancestral type - a smallish, ground-dwelling
bird, with a cone-shaped beak adapted for crushing seeds
...

Due to competition, these original ancestral types would spread out
...
Those finches with variations most suited to the new
environment would survive to reproduce maturity, hence passing on the different and successful
variation to the offspring
...

These species would have fundamental differences such that when placed with other species, also
related to the common ancestral type, they would not interbreed
...
These favourable characteristics will then be passed on
from generation to generation
...

- Speciation involves the splitting of a single evolutionary lineage into two or more genetically

-

-

independent ones
...
The splitting up of one gene pool into two or more separated gene pools (genetic
separation)
...
The diversification of one phenotypic form into many (phenotypic differentiation)
...

Selective pressures may act on two populations (light, dissolved oxygen, current)
...

Speciation occurs when new species develop - presumably from a common ancestral species
...

ALLOPATRIC SPECIATION is the most common whereby one population becomes isolated
from the rest of the species and evolves by macroevolutionary change
...

For example, organisms may migrate to a new environment such as Darwin’s Finches
...

Organisms may be geographically isolated by such events including a continental drift or climate
change
...
This could lead to the formation of a subspecies if the populations are still able
to interbreed
...

This happens most commonly in plants where polyploidy occurs
...

If these individuals are well adapted they will spread through the existing species as a separate
‘spontaneous’ species
...
This usually occurs where groups
within a species occupy different habitats and become reproductively isolated
...

Mechanisms that result in reproductive isolation before breeding occurs are called PREZYGOTIC ISOLATING MECHANISMS and include:
1
...

2
...

3
...

4
...

If two isolated species mate, then the following may occur which prevents the survival and
reproductive fitness of the offspring - these are called POST-ZYGOTIC ISOLATING
MECHANISMS:
1
...

2
...

3
...

4
...


Patterns of Evolution
- ADAPTIVE RADIATION is where species develop from a common ancestor
...


- CONVERGENT EVOLUTION is where organisms with different ancestors came to be more
-

-

alike because they were adapting to similar environments (similar to analogous structures)
...

PARALLEL EVOLUTION occurs when, after speciation, the physical appearance, or
phenotype, of the species remain similar but the genotype is different
...

GRADUALISM implies that evolution is a gradual ongoing process of change and adaptation
...

The fact that the fossil record shows the sudden extinction of some species, the sudden
emergence of new species and the unchanged continuation of others, has led to the idea that
evolution has occurred in a series of ‘jumps’
...

These periods were then interrupted by sudden change, which consequently led to extinction and
the emergence of a new species: those that were best able to adapt to the new environment
...
This affects the selective pressures that are acting on other

-

species and therefore their course of evolution
...

Other examples include clearing of habitats, hunting and over exploitation of species,
domestication and breeding of various agricultural crops and addition of chemicals to the
environment
...
Immune variants

-

-

survive in greater number to breed and increase their frequency in the population over several
generations
...

The aim of SELECTIVE BREEDING is to produce a new variety (e
...
dog breeds) or to
increase the yield of an old one (egg production)
...
Offspring with the selected
trait are singled out for breeding and so on
...


Human Evolution
- Humans are primates - one of the species of ‘great apes’
...

- Throughout evolutionary history, many different hominid species have existed
...

- With the development of new biochemical technologies, gorillas and chimpanzees have been

-

-

-

reclassified as hominids
...

The African apes are shown by anatomical and molecular comparisons to be the closest living
relatives of humans
...
5-4
...

These hominids walked upright and they were either direct ancestors or an offshoot of the line
that led to modern humans
...

Also living in Africa at the time was A
...
robustus, a hominid with robust bones, large teeth, heavy jaws and thought to be a
vegetarian
...
7 million years ago, HOMO ERECTUS, believed by some to be descended from H
...

They also had much larger brains and were probably the first to use fire and the first to move out
of Africa
...


- Australian palaeontologists announced the discovery of stone tools dated at about 800,000 years
-

-

-

-

old and belonging to H
...

The discovery provided strong evidence that H
...

The NEANDERTHALS were large-brained and heavily built, probably adapted to the cold
conditions of the ice ages
...

In December 2000, scientists unearthed the fossilised remains of a hominid dating back 6 million
years
...
7 million years ago
...

Genetic studies indicate that the last common ancestor between chimpanzees and humans, known
as the MIOCENE APE, lived 5 to 10 million years ago
...

Dispute continues over the hominid status of Ramapithecus, the jaws and teeth of which have
been found in India and Kenya in late Miocene deposits, dating between 14 and 10 million years
ago
...

It is thought to be close to the initial divergence of the great apes and humans
...
sapiens emerged from H
...

The REGIONAL-CONTINUITY MODEL, according to which selection pressures led to the
emergence of similar advances types of H
...
erectus in different parts of the world
at around the same time
...

Analysis of DNA in recent human populations suggest that H
...

The oldest known fossils come from Africa, dating 100,000-150,000 years ago
...
5% differ
between humans and the great apes
...

For natural selection to work on a given population, there must be variety within that population
and competition for strategic resources
...

RANDOM GENETIC DRIFT is the loss of alleles from a population’s gene pool through
chance
...

GENE FLOW occurs through interbreeding: the transmission of genetic material from one
population to another
...

CREATIONISM accounts for biological diversity by referring to the divine act of creation as
described in Genesis
...

INTELLIGENT DESIGN states that modern physics and cosmology have uncovered evidence
for intelligence in the structure of the universe and this intelligence seems to act with us in mind
and that the universe as a whole shows evidence of design
...
Dense hair or fur covering body
...
Flatter face
...
Warm-blooded
...
Live young
...
Suckle
...
Infant dependence
...
Social life
...
Play
...
Observation and imitation
...
Pecking order
...

They are part of the family Hominidae, ate plants and meat, walked upright and had larger brains
than apes
...

Theories include tool use, energy efficiency, radiator theory, body temperature, habitat
variability, reproduction and canine reduction
...
Brain size
2
...
Hunting
4
...
erectus)
5
...
Built shelters
7
...
Language

- HOMO HABILIS had a 612 cc brain, lived 2
...
6 million years ago, first toolmaker,

-

prognathic face, brow ridge, probable meat-eater, possibly arboreal, discovered in 1960 by
Leakeys and had no speech
...

The earliest Homo erectus remains indicate rapid biological change
...
habilis to H
...

H
...
habilis
...

Dubois calls it Pithecanthropus erectus initially, also dubbed ‘Java Man’
...

Dates from 1
...
C
...

Acheulean tool industry
...
erectus was so successful because they had less sexual dimporphism (possible pair bonds,
marriage), less hair on body (wearing of furs) so ability to live further north
...

- Culture is main reason H
...

- Organisation for hunting, ability to protect against predators, control of fire, possible campsites
-

-

-

-

and tools
...

Massive brain - about 1400 cc on average
...

Later remains show decrease in robustness of the front teeth and face, suggesting use of tools
replaced teeth
...

Homesites - in caves, also in the open (near rivers, framed with wood and covered with skins)
...

H
...
sapiens for at least 20,000 years, and it is assumed that
Neanderthals interbred with H
...
sapiens or H
...

HOMO SAPIENS were around the Archaic age, from 100,000 to 35,000 years B
...
Sometimes
called Homo sapiens and Homo sapiens neanderthalensis
...

CRO-MAGNON MAN were around 35,000 to 17,000 years BC in western Europe
...

Not a different species, just old Homo sapiens from Europe
...
sapiens culture included art, with traces of art found in beads, carvings and
paintings
...

Female figurines, called ‘venuses’, these depicted women with large breasts and broad hips
...

H
...

Tools included from cores to blades, specialisation, composite tools, bow and arrow
...

Socially organised into hunter-gatherer analogy including small group, low population density,
nomadism and kinship groups
...


- Modern humans vary in skin colour, hair colour and eye colour
...

It is the accumulation of differences between groups which can lead to the formation of new
species, usually a result of diffusion of the same species to different and isolated environments
which blocks the gene flow among the distinct populations allowing differentiated fixation of
characteristics through genetic drift and natural selection
...

Assuming that phenotypic differences are genetically determined, such selection should lead to
evolutionary change and, indeed, it has
...
This
success is strong proof that selection is an effective evolutionary process
...

A METAMORPHIC ROCK is a result of a transformation of a pre-existing rock
...

Examples include marble, slate, gneiss and schist
...

Examples include obsidian, granite and pumice
...




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