Sample PowerPoint Teaching presentation from Preliminary Biology course. Unit 8.4" "The Evolution of Australian Biota".

1. Evolution of Australian Biota 3
• Discuss examples of variation between
members of a species (syllabus)
• Identify the relationship between variation
within a species and the chances of
survival of species when environmental
change occurs (syllabus)

2. Variation and Heredity
• Variation refers to the differences in the
characteristics of individuals within a species. Eg
offspring may resemble their parents but they are
not identical to them.
• Heredity is the transmission of similar
characteristics from parents to offspring.

3. Variation and Heredity
• Within a population, variation may have one of three
origins: (i) genetic eg eye
colour; (ii) environment e.g. body
builders; (iii) a combination of genes and the
environment e.g. the fur of many arctic animals
changes to white when located in low temperatures.
• The ability of fur changing colour is hereditary but it is
only operative in very low temperatures.
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5. Survival of populations
• The variation in the gene pool (all possible varieties) of a
population determines their chance of survival.
• If there is a sudden change in the environment, individuals
possessing a variation (random) that is advantageous to the
change are more likely to survive the changed conditions.
Those that survive are more likely to reach sexual maturity
and pass their favourable characteristics to their offspring.
Individuals with less favourable variations will eventually be
eliminated from the population (out-competed).
• If individuals within the population become so different
that they can no longer interbreed with individuals from
the original population to produce fertile offspring, then
the population is considered a new __________.

7. • For Example....
• Let's say a disease sweeps through a population. Those
individuals with a natural resistance to the disease would
survive.
• These ANIMALS have adapted to the new environment (i.e.
they have adaptations which allow them to survive):
• Koalas in northern Australia have smaller bodies, shorter hair
and a lighter coat colour than koalas in southern Australia.
Larger mammals tend to survive better in colder climates due
to having less body surface area compared with their volume
so they can conserve heat more efficiently.
• Snow gum trees grow in the Snowy Mountains and as altitude
increases the trees decrease in height, leaves become shorter
in length and fruit increases in size and frost resistant
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Survival of populations

8. 8
Survival of populations

9. 9
Survival of populations

10. Charles Darwin and Alfred Wallace
• In 1858 Charles Darwin and Alfred Wallace proposed
their theory of evolution by __________ __________.
The theory centres around four main points:
1. Variation – individuals within a population that
reproduce sexually, show variations that can be passed
from one generation to the next.
2. Natural selection – selective pressure (change in the
environment) puts constraints on organisms (eg
resources become limited). These constraints are called
selective pressures and determine which individuals
are best suited to the prevailing conditions.

11. Charles Darwin and Alfred Wallace
3. Survival of the fittest – more individuals are produced
within a population than can survive. Those individuals with
favourable variations have a greater chance of survival because
they out-compete those with less favourable variations.
Organisms surviving reproduce and pass on their genetic
variations on to their offspring.
4. Isolation – if a population is isolated from the original
population, interbreeding will be prevented over a period of
time. This is important for the evolution of a new species to
occur.