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Classification
To be a living thing, one must perform the 7 vital functions;
1
...
Nutrition; intake of food for energy
3
...
Sensitivity; respond to changes within the body and the surrounding
environment
5
...
Growth; increase in body size using materials in food
7
...

These are classified into groups based on structural similarities and evolutionary
relationships; Taxonomy
...

The 7 major taxonomic categories are;
Kingdom

Most general

Division/phylum
Class
Order
Family
Genus
Species
Heterotrophic – organisms feed on organic material, usually are able to move
Autotrophic – organisms synthesise their own organic requirements from inorganic
compounds, usually stationary
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•

Monera: unicellular/multi cellular, immotile, have cell walls, no membranebound organelles, no visible feeding mechanism

•

Protoctista: unicellular/multicellular, motile by cilia or flagella, have cell walls,
have membrane-bound organelles, heterotrophic/autotrophic

•

Fungi: multicellular, have cell wall, no chloroplasts, absorb pre-digested food
from decaying matter

•

Plantae: multicellular, move by cilia or flagella, have cell walls and membranebound organelles, photosynthesise

•

Animalia: multicellular, move by cilia or flagella or muscles, have membranebound organelles, no chloroplasts or cell walls, heterotrophic

Species concept
•

Sexually reproducing; a group of organisms which can interbreed freely
among themselves and produce fertile offspring

•

Asexually reproducing; a group of organisms which are closely related to one
another

Taxonomy
•

Sexual reproduction: these organisms belong to the same species if they
interbreed under natural conditions
...

Homologous structures; differ in function but have a similar anatomy
indicating that the organisms descend from common ancestors e
...
finger
bones of dolphins, bats, seals and humans
...

To distinguish between closely related species, taxonomists study microscopic
details
...
PCR is a technique that enables scientists to amplify DNA form the
remains of extinct organisms and compare it with that of their living relatives
...
E
...
Canis

familiaris and Canis lupus
...
g
...
filfolensis
Whenever the identity of a species is uncertain e
...
Drosophila sp
...
It is based on
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how people choose how many and which characteristics are important and which are
not
...

In an artificial classification only one characteristic is chosen
...

Dichotomous keys
They are used to identify and classify living organisms
...
One cannot use colour in a dichotomous key and number of hairs
or lengths
...

Biological diversity
Biological diversity refers to the variety of life in all forms, levels and combinations
...
Species diversity; the frequency and diversity of different species including
domesticared and cultivated ones
...
Ecosystem diversity; the variety and frequency of different ecosystems
3
...
This enables
evolutionary development
...
A virion consist of
a core (DNA), capsid (protective coat made of protein around the core made up of
smaller subunits called capsomeres) and some also contain an envelope (lipoprotein
layer)
...
They
have specific hosts and cause a wide range of diseases
...
They also do
not respond to changes in the environment
...
g
...
Their life cycle;
1
...
Pins and end plate anchor virus to cell surface
3
...
Viral DNA replicates and takes over protein-synthesis machinery of the host
cell, forcing the cell to produce new protein coats
...
DNA and protein coats assemble and make new phage particles
6
...
New phage particles are released to infect more bacteria
This is a lytic cycle, they complete it without a break
...
They are called
provirus (prophage)
...


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In response to changes in the host’s environment, it is activated again and
completes its life cycle, this is called lysogenic cycle
...
g
...
They can convert RNA into DNA using the enzyme
reverse transcriptase
...
Their life cycle;
1
...
Virals glycoproteins attach to specific receptor proteins in the membrane
3
...
Viral RNA and reverse transcriptase are released into host cell
5
...
The DNA copy enters the nucleus and inserts itself into the host DNA
7
...
New RNA and viral proteins are produced using the host’s protein
synthesising machinery
9
...
Viral particles bud off from the host’s membrane by exocytosis

Monera
Single celled prokaryotic cells, they are ubiquitous (found everywhere) and they
cause the decay of organic material and help in the recycling of nutrients
...

E
...


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The slime capsule is a coating of polysaccharides that allows the bacteria to stick to
host cells or to each other to form colonies, to stick to surfaces and the escape
attack by the defense system of the body
...
g
...

Bacteria can be gram positive or gram negative according to what their cell wall is
made up of
...

It involves heat-fixing bacteria to a clean microscope slide and then flooding it with
crystal violet
...
Finally the smear is counter-stained with a red stain such
as safranin
...

Gram-positive bacteria stay purple
...
Peptidoglycan layers are
connected by bridges of amino acids
...
They have two unique
regions which surround the cell membrane
...
The periplasmic space which separates the lipopolysaccharide layer from the
peptidoglycan layer
...

2
...


They

contain

of

polysaccharides and toxins which are responsible for most of the pathogenic
effects
...

Photosynthetic membranes contain photosynthetic pigments and are the site of
photosynthesis
...

Flagellum is a simple hollow cylinder made of protein which is attached to the cell
wall
...

Pili are fine protein rods found on Gram-negative bacteria which attach to cells or
surfaces and help in sexual reproduction
...

Endospores are extremely resistant which contain genetic material and a few
enzymes but are metabolically inactive
...
DNA replicates while the DNA molecule may be held in
position by a mesosome
...
The cells come into contact
by conjugation and the DNA is transferred between the cells through a hollow sex
pilus
...

Nutrition
•

Chemo-autotrophs; use CO2 as a source of C but obtain their energy from
chemical reactions
...
E
...
saprotrophs,
mutualists and parasites
...


•

Photo-heterotrophs; only purple non-sulfur bacteria

Most bacteria are chemo-heterotrophs
...
Organisms that are able to be both are called facultative anaerobes
...

Evidence;
1
...

2
...

3
...
They are surrounded by a double membrane, and the composition of the
inner membrane is like that of a prokaryotic cell
...
The internal structure and biochemistry of plastids is similar to that of
cyanobacteria
6
...

7
...


Prokaryotic and eukaryotic cells
Two types of cells, the eukaryotic cells evolved from prokaryotic cells
...
They lack a true nucleus
...


Algal protoctists:

-

Photosynthetic eukaryotes
...

Phylum chlorophyta (green algae)
-

Gave rise to terrestrial plants (cell walls contain cellulose, chlorophyll a
and b, carotene and xanthophylls, store starch)

-

Motile stage/are motile

-

i
...


Chlamydomonas: unicellular, motile: two flagella, single cup-shaped
chloroplast

iii
...


-

Store carbs as soluble laminarin and mannitol

-

Marine

-

Filamentous or thalloid, often large

-

Provides

food,

shelter

and

breeding areas
i
...
g
...


Unicellular, heterotrophic

Complex cell structure with a macronucleus and a micronucleus

Paramecium
-

Stagnant/slow-flowing water, with decaying organic matter

-

Has cilia

-

Has trichocysts (fine threads can be discharged which are probably
used for anchorage during feeding)

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-

Beneath the pellicle is a layer of ectoplasm while the bulk of the
cytoplasm is in the form of endoplasm – most organelles are found
...
Both the oral groove and gullet are lined with cilia
which direct food towards the cytostome
...
Food is digested and products are absorbed into the
cytoplasm
...

Contractile vacuoles pump out water by active transport to maintain a constant
concentration of water molecules inside the cell (osmoregulation)
...


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The macronucleus is polyploidy and controls metabolic activities apart from
reproduction
...

-

Paramecium reproduces asexually (binary fission)

-

Two paramecia can also exchange genetic material by conjugation


Fungi
Eukaryotic, non-motile e
...
yeasts
Structure
Body consists of a mass of fine, tubular, branching threads (hyphae), the whole
mass is called mycelium
...

They do not have true cells; the cross-walls are interrupted by septa
...
They may have two or more nuclei (coenocytic)
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Nutrition
Absorptive heterotrophic: they secrete enzymes outside its body on its food and
digestion takes place outside the body, the nutrients are then absorbed into the
fungal hyphae
...

Carbohydrates are stored as glycogen
...
The
spores are dispersed by wind or water
...

Yeast cells reproduce asexually by budding
...
The
fungus protects the alga from dessication and high light intensities while also
contributing to water and mineral salts
...


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Mycorrhizae
Associations between fungi and plant roots
...


Animalia
-

Multicellular, heterotrophic

-

Sexual reproduction

-

Lack cell walls

-

Motile

-

Make rapid responses to external stimuli

-

They develop from a ball of cells (blastula) that forms in early embryonic
development

Multicellular, diplobastic, triploblastic organisation
Cnidarians have only two germ layers – diplobastic organisation: endoderm and
ectoderm
...

Bilateral symmetry: can be divided by a single line into roughly mirror-image right
and left halves with an upper surface and a lower surface
...

Cephalisation means that there is a head and therefore a concentration of sensory
and feeding organs, and centres of neural integration near the anterior end of the
animal which first encounters the environment
...


Cnidaria
ü Diploblastic:
-

Outer ectoderm face the environment

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-

Inner endoderm facing the enteron, the mouth through which both
ingestion and egestion occurs
...
Undigested material is expelled through the mouth
...
All cells are in direct
contact with the water so gaseous exchange can take place efficiently
...

ü Radial symmetry: body parts are arranged in a circle
...
g
...
Within these cells are
nematocysts – capsules containing long spirally coiled hollow threads
...
They also serve as a
defense
...


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The ectoderm also contains sensory cells which connect with nerve cells
forming a nerve net
...

ü Reproduction: asexually through budding – formation of small outgrowths
which pinch off and begin to live independently
...
The fertilised egg often develops into a
free-swimming ciliated larva that settles and becomes a tiny polyp
...
Cnidarians have a very low metabolic rate since the bulk of the body is made
up of largely inert mesoglea
...

2
...

Class Hydrozoa
These are marine and polyp-dominant in life cycle
...
It has well developed oral
tentacles
...
They overcome
this by their flattened body, maintaining a large SA:V
...

They have a branched gastrovascular cavity that digests food and distributes
nutrients to all parts of the body
...
It consists of flame cells containing beating cilia which drive
liquids through the system
They reproduce sexually and asexually
...
A parasitic flatworm can reproduce through selffertilisation
...
They can also reproduce by separating into
two halves, and each regenerate the missing parts (fragmentation)
...
g
...
Cuticle is absent, gastrovascular cavity present, sense organs in
adult
...
The
prey is sucked up though a muscular tube called pharynx
...
g
...
Its body is
divided into proglottids
...

They have a thick cuticle to protect the host against the digestive juices, no
gastrovascular cavity which absorbs pre-digested food from host by diffusion across
the body wall
...

The pork/beef tapeworm – Taenia
The host becomes infected when meet with cysts is eaten
...
The eggs might end up in the cow again where they
burrow through the intestinal wall, travel through the blood stream and burrow into
muscle tissue where they form cysts; repeating the cycle again
...

ü Acoelomate: no coelomic cavity exists – the mesoderm completely fills the
space between the ectoderm and endoderm and forms a solid middle layer
(flatworms)
...

ü Coelomate: completely lined, the lining is called the peritoneum – portions
of the peritoneum which connect with gut wall to the body wall across the
coelom are called mesenteries and these suspend organs within the coelom
...
In the earthworm it acts as a hydrostatic skeleton, providing locomotion,
protects the body and supports it
...
It serves as a protective buffer between the organs and the external
environment
...
Permits space for development of sexual organs
4
...
Muscular movements of the body wall, can be separated from muscular
movements of the gut wall
...
It permits longer digestive tracts to develop
7
...

However it reduced the efficiency of diffusion, therefore circulatory systems were
developed
...


Molluscs
•

Triplobastic

•

Bilateral symmetry

•

Coelomate

•

Unsegmented

•

Body soft, moist and muscular, built from three-structural components:
(1) Head: showing cephalisation, the nervous system consists of ganglia
connected by nerves
(2) Dorsal visceral mass: includes internal organs
(3) Ventral muscular foot: locomotion
...
In
many species, the mantle secretes a protective covering, the shell
...


•

Sexual

reproduction:

some

are

of

separate

sex,

and

others

are

hermaphrodites
•

Adaptive radiation: divison of body has allowed diversification
...


Most marine gastropods use their gills for gas exchange
...

Metameric segmentation
It is an evolutionary device for increasing body size using a minimum of new genetic
information
...
A tagma is a distinct section of an arthropod,
consisting of two or more adjoining segments
...


•

Definite cuticle

•

Chaetae: hair-like structures made of chitin which are inserted into the dirt
allowing the body to be pulled forward

Class Polychaeta
Marine, segmented, no clitellum, cuticle, distinct head (cephalisation)
...


Chaetae numerous on lateral extensions of the body called parapodia – the
parapodia have a good blood supply and function as the animal’s gaseous exchange
surface
...
It has no distinct head
...
Food drawn into the mouth by the action of the muscular
pharynx is stored in a crop and is ground up in a thick, muscular gizzard
...

They have a clitellum, which helps in the process of copulation and secretes a
cocoon in which the eggs are deposited
...


Exoskeleton
1
...
Anchorage for muscles
3
...
Low density; allows flying
5
...
Body size is limited; breathing mechanism
2
...
Ecdysis is required
...
In some
organisms the head and thorax fused forming cephalothorax
...

•

Incomplete metamorphosis: each successive larval form (nymph or instar)
looks more and more like the adult
...


Incomplete metamorphosis

complete metamorphosis

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This enables it to live in different habitats and exploit different sources of food
...


Echinodermata
ü Triploblastic
ü Coelomate: lack a circulatory system
...

ü Symmetry: pentamerous radial symmetry
ü Mode of life: marine
ü Tube feet and water vascular system: they move on numerous tube feet
...

Sea water enters through the madreporie and is conducted to a ring canal
...
Many lateral canals
extend into the tube feet
...
These contract and push
water into the tube feet causing them to extend
...


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ü Gas exchange: occurs through the thin walls of tube feet, numerous tiny skin
gills project through the epidermis
...
They have projections, spines through the outer
layer of the skin
...
Around the bases of
the spines, pincer-like pedicellariae help keep the body surface free from
debris and protect the gills
...

ü Mouth or oral surface, anus on aboral surface: it can push its stomach out
through its mouth and then through the narrow spaces between the shells of
the bivalve
...
This is absorbed for complete digestion
...
Sea stars can also regenerate lost parts, provided that the part of the
central body is attached to it
...
g
...
g
...
Many sea urchins are herbivorous and feed on algae using a complex
rasping structure or on small organic particles
...
It
increases internal support and locomotory power
...

ü Pharyngeal (visceral) clefts: slits in the pharynx, they form functional
respiratory openings
ü Dorsal, hollow, nerve cord (spinal cord): neural structure lying dorsal to the
digestive tract that develops a thickening at its anterior end that becomes a
brain
ü Post-anal tail
ü Segmental muscle blocks (myotomes): on either side of the body
ü Limbs formed from more than one body segments
...
It provides:
-

Support for the body

-

Attachment site for muscles

-

Protection for the delicate nerve cord and brain

Animals which have this vertebral column is called a vertebrate, animals which do
not are called invertebrates
...

Endoskeleton: the backbone is part of a living internal skeleton, capable of growth
and self-repair
...


All vertebrates but fish are tetrapods, they have four limbs
...
This provides the embryo with a fluid-filled cavity, in which it can
develop on land
...

Yolk sac: develops an outgrowth and encloses the yolk, a food supply which is
gradually absorbed by blood vessels of the yolk sac (protein food source)
...
This provides the embryo
with a fluid environment
...
As the
embryo grows, the amnion is pushed outwards until it fuses with the chorion
...


Mammalia
-

Endothermic

-

High metabolic rates
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-

Fur which insulates the body

-

Four-chambered heart increases the amount of oxygen delivered to tissues

-

Two pairs of pentadactyl limbs

-

External ears, nares and vibrissae used for tactile sensing

-

Internal fertilisation

-

They are amniotes (produce a fluid-filled sac around the embryo)
...
g
...


In the marsupials, the period of uterine development is short and the young are
born at a very immature stage
...

Placental mammals; retain their young in the uterus for a much longer period
...

-

Mammary glands used by females to suckle their young

-

Skin has sweat, scent and sebaceous glands

-

Diaphragm between thorax and abdomen
...


Transition from an aquatic to a terrestrial mode of life
AMPHIBIANS:
-

Some species have lungs that supplement the gills

-

Some have fleshy fins to drag themselves to a better pond

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