Topic 4 - Evolution Flashcards
What is evolution?
● A gradual change in the inherited traits within a population over time
● Occurs 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
- Antibiotics act as a selection pressure
- Mutations gives a bacterium antibiotic-resistance
- If an antibiotic is administered, the bacterium is better adapted and
survives, whilst other bacteria are killed - Bacterium reproduces, passing on its resistant variant
- 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?
‘Ardi’ - 4.4 million years old
● ‘Lucy’ - 3.2 million years old
● Leakey discovered 1.6 million year old fossils
What clues does ‘Ardi’ give scientists about human evolution?
Female hominid fossil. She shows phenotypic traits which encompass characteristics of both humans and apes:
● Ape-like characteristics e.g. long arms, large big toes
● Human-like characteristics e.g. the structure of her bones suggests that she walked upright
What clues does ‘Lucy’ give scientists about human evolution?
Female hominid fossil. She shows phenotypic traits which are more human-like than that of ‘Ardi’:
● The 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?
He discovered many hominid fossils.
The 1.6 million year old fossil ‘Turkana Boy’ showed traits comparable to that of modern-day humans e.g. similar brain size.
How has the development of stone tools provided evidence for evolution?
● Correlation between the development of more complex tools and an increase in brain size
● Primitive tools are older than more complex tools. Brain size has increased over time ∴ as brain size increased,
advancements in tool use were made.
