Topic 4 – Natural Selection and Genetic Modification-Evolution Flashcards
what is evolution?
gradual change in inherited traits within population over time
due to natural selection
Outline the theory of natural selection
- Genetic variation exists due to spontaneous mutations
- Selection pressures (e.g. competition, disease) exist
- Random mutation gives an organism a selective advantage
- Organism is better adapted to the environment and survives
- Organism reproduces, passing on its beneficial alleles
- Frequency of advantageous alleles increase
Why does competition between organisms in a habitat exist
The resources within a habitat required for survival are limited
give some examples of competition between organisms within a habitat

Competition between animals for food, shelter, mates etc.
Competition between plants for light, water, minerals etc.
describe how antibiotic resistance in bacteria can be used as an example to illustrate the process of evolution

Genetic variation exists due to spontaneous mutations
2. Antibiotics act as a selection pressure
3. Mutations gives a bacterium antibiotic-resistance
4. If an antibiotic is administered, the bacterium is better adapted and
survives, whilst other bacteria are killed
5. Bacterium reproduces, passing on its resistant variant
6. Frequency of antibiotic-resistant allele increases
Why is the development of antibiotic resistance in bacteria a good study for evolution?
Bacteria reproduce very rapidly, allowing the first-hand observation of evolution
How can the observation of fossils provide evidence for evolution?

Older fossils (found in rocks deeper in the ground) contain simpler organisms. Newer fossils (found closer to the surface) contain more complex organisms. Comparisons of fossils show that simple organisms evolved into more complex life forms. Fossils can be organised into chronological order, allowing the changes in organisms over time to be observed
Describe the role of Darwin in the development of the theory of evolution by natural selection
Studied a variety of organisms whilst travelling around the world on the HMS beagle
Noted that traits can be passed from parents to offspring
Proposed the idea of ‘survival of the fittest’
Established the theory of natural selection and published his ideas in ‘On the Origin of Species’
Describe the role of Wallace in the development of the theory of evolution by natural selection
he proposed a theory of natural selection that was similar to Darwin’s, although the mechanisms were different
He gathered greater evidence (e.g. studying warning colouration in butterflies) to support the theory
How has the theory of evolution by natural selection impacted modern biology and society?
Enables the classification of organisms into taxa
influences modern medicine by emphasising the importance of finishing antibiotic treatments and the need for the constant production of new antibiotics
Highlights the importance of high genetic diversity in habitats which aids conservation projects
What fossils have provided evidence for human evolution?
Ardy 4.4 million
Lucy 3.2 million
Leakey discovered 1.6million years old fossil
what clue does ardi give scientists about human evolution
Female fossil. shows phenotypic traits which encompass characteristics of both humans and apes:
long arms, large big toes
the structure of her bones suggests that she walked upright
what clues does ‘Lucy’ give scientists about human evolution?

Female fossil. shows phenotypic traits which are more human-like than that of ‘Ardi’:
structure of bones in her legs and feet are more adapted to walking than climbing
However, her brain size is closer to that of an ape’s
How did Leakey’s findings provide evidence for human evolution?
discovered many homind fossils.
1.6 million year old fossil ‘turkana boy’ showed traits comparable to that of modern day humans
ow has the development of stone tools provided evidence for evolution?

Correlation between development of more complex tools, also increase in brain size
Primitive tools are older than more complex tools.
Brain size has increased over time so, as brain size increased, advancements in tool use were made.
