Unit 4 - Variation and Evolution

Question 1

Give 4 sources of evidence for evolution

Answer 1

-Palaeontology (fossils)
-comparative anatomy
-comparative biochemistry
-comparative embryology

Question 2

How can the relative age of fossils be determined?

Answer 2

-over time sediment is deposited to form rock strata
-recent rock strata are found at the top and older rock strata are found at the bottom
-radioisotope dating can be completed on fossils to date rock strata

Question 3

How do fossils provide evidence for evolution?

Answer 3

-fossils of the simplest organisms are found in the oldest rocks
-fossils of more complex organisms are found in more recent rocks
-allow relationships between extinct and living organisms to be investigated
-sequence in which organisms are found matches ecological links

Question 4

What is comparative anatomy?

Answer 4

The study of similarities and differences between organisms’ anatomy

Question 5

What are homologous structures?

Answer 5

A structure which appears superficially different (and may perform different functions) in different organisms but has the same underlying structure

Question 6

What is divergent evolution?

Answer 6

Species diverge over time into two different species, resulting in new species becoming less like the old one

Question 7

What is comparative biochemistry?

Answer 7

Similarities and differences between the chemical make up of organisms

Question 8

How does comparative embryology provide evidence for evolution?

Answer 8

-embryos of different animals looks very similar
-shows animals develop in a similar way
-implies the process of embryonic development has a common origin

Question 9

Define interspecific variation

Answer 9

Differences between different species

Question 10

Define adaptation

Answer 10

Characteristics that increase an organism’s chance of survival and reproduction in its environment

Question 11

What are the 3 types of adaptations?

Answer 11

-structural
-behavioural
-physiological

Question 12

What are physiological adaptations?

Answer 12

Adaptations relating to processes that take place within an organism

Question 13

Define analogous structure

Answer 13

Structures which have adapted to perform the same function but have different (genetic) origins

Question 14

Define convergent evolution

Answer 14

Organisms evolve similarities because the organisms adapt to similar environments or other selection processes

Question 15

Why do organisms from different taxonomic groups show similar structures?

Answer 15

-they adapt to similar environments or other selection pressures

Question 16

Give an example of two sets of organisms from different taxonomic groups that are similar

Answer 16

Marsupials and placental mammals in Australia

Question 17

Define gene pool

Answer 17

All genes and their allelic forms in a given population

Question 18

Define selection pressure

Answer 18

Any factor for which there is competition between individuals in which some will survive and some will die

Question 19

Describe the effect of the industrial revolution on peppered moths

Answer 19

-before the industrial revolution peppered moths were light in colour
-after the industrial revolution peppered moths became darker
-soot caused the bark of trees to get darker
-dark colour moths were better camouflaged
-light moths were eaten

Question 20

What did Darwin observe about finches on Galapagos Islands and how did this support his Theory of Evolution by Natural Selection?

Answer 20

• Finches on different islands had different overall size, claw size, beak size, and beak shape
• Selective pressure of different food sources available on different islands caused finches to adapt differently on each island
• E.g. long thin beak suitable for catching and eating insects vs. large powerful beak suitable for crushing nuts
• All finches originally same (common ancestor) -> specific variations on each island were favoured -> these advantageous individuals survived and reproduced -> hence why Darwin observed the distinct differences on each island

Question 21

What did Darwin observe about Australian flora and fauna?

Answer 21

Fauna: a rat-kangaroo and platypus in Australia occupied ecological niches similar to those of the rabbit and water rat in the Northern Hemisphere — similar ecological niches in different parts of the world were occupied by very different species

Flora: Eucalypts are evergreen — an adaptation as a result of the harsh environment they were in

Question 22

punctuated equilibrium vs gradualism (gradual process of natural selection)

Answer 22

Punctuated equilibrium:
- Evolution proceeds rapidly in bursts for short periods of time, intermittent with long periods of stability (no evolution)
- Lack of intermediate forms
- Supported by gaps in fossil record

Gradualism:
- Continuous evolution at a constant pace over a long period of time
- Intermediate forms — gradual accumulation of mutuations/variation

Question 23

What is speciation?

Answer 23

The formation of new species separate from the rest of the population due to geographic and sexual isolation

Question 24

Evolutionary change in cane toads?

Answer 24

• Fast-moving cane toads interbreed and produce offspring with longer legs, faster
• Cannibalism

Question 25

Explain the extinction of Australian megafauna?

Answer 25

Climate change:
- Continent dried out after last ice age -> less surface water -> megafauna reliant on sufficient supply of water died out
- Sudden change in temperature -> breeding seasons affected + food sources may have become less available -> died out

Humans:
- Hunted megafauna, were successful predators

Question 26

Explain the extinction of the Tasmanian tiger

Answer 26

Competition with dingos (introduced species), habitat loss, disease, human killings