Slides in this set

Slide 1

Preview of page 1

Natural Selection: Individuals compete for limited resources. Individuals
in a population show natural variation. Individuals with characteristics best
suited to their environment are more likely to survive to reproduce.
`Successful' characteristics are inherited.
· An organisms DNA can change, this is called a mutation. If the mutation
effects the gene it is passed on.
·Evidence for evolution comes from the fossil record. Fossils show how
much, or how little, organisms have changed over time.
·One of the problems with the fossil record is that it contains gaps.
· The main factors that cause extinction are : changes to the environment,
new diseases, new predators and new competitors!
· Desert animals adapt to save water and have large surface area to volume.
(helps to lose body heat)
· Artic animals adapt to reduce heat loss by being insulated and have a small
surface area compared to volume.
· Plants adapt to hot climate also by having a small surface area and spines
instead of leaves.
· Humans also compete for space and resources.
· The impact of the population growth is that: more waste is being produced
(water, land and air), raw materials are being used up and more pollution is
being caused.
· The land is being used for buildings, farming, dumping waste and
· The main land polluters are: fertilisers, sewage and toxic chemicals.
· The main air polluters are smoke, carbon dioxide, carbon monoxide and
sulphur dioxide.
· Lichens cant grow in polluted areas, thus showing the pollution level.
· Deforestation cause a loss of biodiversity and adding to global warming.
·Climate change shows that the earth is getting warmer. The rise in
temperature has caused: sea levels to rise, ice caps to melt, disruption in
food production and has changed weather patterns.
·The extra methane and carbon dioxide adds to the greenhouse effect and
traps the heat from the sun. this created a insulation layer and the earth is
gradually getting warmer.
· Deforestation, car exhaust, burning of fossil fuels and industrial
processes all add to this.
· Sustainable development means improving our quality of life without
damaging the quality of life of future generations.…read more

Slide 2

Preview of page 2

Sexual Reproduction is when a male and female sex cell gametes fertilise
as the nucleus fuse together and make the offspring.
· Sexually reproduced offspring inherit features from both parents and get
23 chromosomes from each parent.
· Asexual Reproduction doesn't need more than one sex cells, it only needs
one parent and the offspring has identical genes to the parent. The
offspring is made by the cell and its chromosomes dividing into two.
· A disadvantage of asexual is that they are unable to adapt when the
environment changes.
· There are four main methods of Cloning: Cuttings, tissue culture, embryo
transplants and adult cell cloning.
· Taking cuttings is when a branch from the parent plant is cut off, its
lower leaves removed and the stem planted in damp compost. It is quick,
easy and ideal for home gardeners.
· Tissue culture is when you take one cell or ex-plant from a plant and grow
it into a whole one. They have to be put into a growth medium and have the
correct amount of light, water and temperature. It is quick and uses a small
amount of space.
· sperm and egg cells from the selected animals are taken and artificially
fertilised. The embryo then develops and is split many times to form clones.
These clones are implanted in other animals to produce the ideal animal.
· Adult cell cloning is when you get a female call and ultraviolet light is used
to kill the nucleus, then a nucleus from a normal cell is removed and added
to the damaged female one. The new cell then multiplies and is implanted
into the surrogate mother.
· Genetic Engineering is also used to change an organism. It is when a
useful gene is removed from on organisms chromosome using enzymes, and
the enzymes are used to cut another organisms gene and insert the "useful"
· It is used to create plants and animals that are resistant to viruses and to
help them grow more useful characteristics.
· it is a very controversial issue topic because it is seen as not natural but
may be very beneficial.…read more


No comments have yet been made

Similar Biology resources:

See all Biology resources »