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BIOLOGY UNIT 2

animal cell

extra parts that plants have

Cells pt 1
Yeast cell

bacterial cell

cells may be specialised
to carry out a particular
function

both are single-celled organisms and
they both have a cytoplasm, membrane
and surrounding cell wall
...


Cells pt 2 - Diffusion

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the greater the difference in
concentration the greater the rate of
diffusion
it can only happen if the particles
are free to move (gases and
dissolved substances)
an example of diffusion is when the
smell of cooking spreads
throughout the house

In the lungs, the blood will continue to take in oxygen
from the alveolar air spaces provided the
concentration of oxygen there is greater than in the
blood
...


organs in animals
organ system

organs

tissues

cells

the nervous system
the respiratory system
the reproductive system
the digestive system

organs in plants
plants are multicellular organisms just like animals
...

glucose is used for respiration or
converted to starch or fats/oils for
storage (during nights etc)
glucose is also used to produce
cellulose (strengthens the cell
wall) and proteins such as
enzymes and chlorophyll

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easy to control conditions so the
plants grow in optimum
conditions
artificial light, has a better light
intensity than normal light and
the plants can photosynthesise
during the night too
artificial heat means the plants
can grow at optimum
additional CO2 allows
photosynthesis to occur at
increased rate
paraffin lamps give off heat, light
and CO2
they have to make sure its
economically worthwile

Organisms and their Environment
key things:
-physical factors
affect the
distribution of
organisms
-transects and
quadrats help collect
quantitative data
about organisms in
their habitat

physical factors:
-light
-temperature
-availability of water
-availability of nutrients
-availability of oxygen and CO2
other things could be predators

transects
-a line across a habitat or
part of a habitat
-the line is a rope
-the number of organisms
of each species can be
observed and recorded at
regular intervals along the
transect
quadrats
-should be placed
randomly so a
representative sample can
be taken
-the validity and
reproducibility of the
results increases as more
quadrats are analysed

-this data can be
used to find the
mean, median and
mode values of
organisms in an area
different species live in different levels of
this oak tree because each level has
different physical factors

mean
add all the numbers
together and divide
by the total amount
of numbers

median
put all the numbers in
numerical order, if there
is an odd number of
results then the median
is the middle number,
however if it is an even
number of results then
the median will be the
mean of the two middle
numbers even

mode
the most frequent
number

Proteins and Enzymes

proteins are made from
long chains of amino
acids which are folded
into a particular shape
(active sites)

different types of
proteins:
-structural components of
tissue (muscles)
-hormones
-antibodies
-biological catalysts

the enzymes in the
stomach, work best in
acidic conditions so the
stomach produces
hydrochloric acid (also
kills harmful
microorganisms)
the enzymes in the
small intestine work
best in alkaline
conditions so bile
neutralises the acid to
provide these
conditions

aerobic

Respiration
respiration releases energy for cells
from glucose

glucose + oxygen = carbon
dioxide + water (+ energy)

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during exercise your heart rate and
breathing rate increases

anaerobic
glucose → lactic acid (+ little
energy)
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uses oxygen
happens all the time
most of the reactions
happen in the
mitochondria
this reaction is
controlled by enzymes

energy is used from respiration to:
-plants make amino acids from sugars, nitrates & nutrients
these amino acids form proteins
-animals use this energy to contract muscles, keep warm,

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doesn’t use oxygen
involves the incomplete
breakdown of glucose
not as efficient as aeroic
respiration
the waste product is lactic acid
instead of CO2 and water
muscles become fatigued and
don’t contract efficiently because
there is a buildup of lactic acid
lactic acid is removed by blood
flowing through muscles

anaerobic respiration causes
oxygen debt (the amount of
oxygen needed to oxidise lactic
acid to carbon dioxide and water) this is why we continue to breathe
deeply and quickly after exercise

Respiration during exercise
during exercise muscles
respire more so:
-oxygen and glucose must be
delivered more quickly
-carbon dioxide and water must
be removed more quickly
this happens by increasing:
-heart rate (increases blood flow)
-rate of breathing (increases rate
of gaseous exchange in lungs)
-depth of breathing

animals store glucose
as glycogen
this can be converted
back to glucose during
exercise

plants store
glucose as
starch

DNA and Cell division

meiosis - makes gametes

differentiation
animal cells differentiate at
an early stage and cannot
go back to stem cells
plant cells keep the ability
to differentiate
stem cells
stem cells are
undifferentiated cells
they can be found from
human embryos and bone
marrow
they can be used to treat
parkinson’s disease (ethical issues= embryo has
no choice)

each gamete has a
single set of
chromosomes
mitosis - used for growth and
repair

genetic variation and disorders
in a human body cell there is 23 pairs
of chromosomes in the nucleus, one
of these control gender:
male = XY
female =XX

embryos can be scanned to see if they have
alleles which cause polydactyly or cystic fibrosis
...
The dominant allele will overpower the recessive
allele
...
So everyone has unique
DNA (except for twins)
...


genetic conditions
occur like:
polydactyly,
because they are
caused by a
dominant allele so
it can be passed to
the offspring by at
least one parent
OR
disorders such as
cystic fibrosis
which is caused by
a recessive allele,
which means it will
only be passed on if
both parents have
it, if not the offspring
will become a
carrier
...

simple organisms are found
at the bottom and complex
organisms are found nearer
the top - supports the
theory of evolution

the horse is one of the only
animals that we have a fairly
complete record of
an example of an adaption is:
from multi toed hoof for forest to
single toed hooves for open fields

extinction & speciation
individuals that are poorly
adapted to their
environment are less likely
to survive and reproduce
than those that are better
adapted
...

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the species become separated
they become adapted to their new
environment
they adapt so much that the two separated
groups of the species can no longer
interbreed

new species can occur by:
-genetic variation
-natural selection



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