evolution and speciation

Question 1

A4.1.1—Evolution as change in the heritable characteristics of a population

Evolution is…

Answer 1

Evolution is the change in the heritable characteristics of a population across time

Question 2

A4.1.1—Evolution as change in the heritable characteristics of a population

Distinguish between heritable and acquired characteristics (Comparing Lamarck and Darwin’s theories of evolution).

BASIS OF VARIATION
Mechanism of Change (what causes evolution?)
Rate of Evolution
Concept of Fitness - an organism’s ability to survive and reproduce in its environment
Role of Environment

Answer 2

Lamarkism: Acquired characteristics during an organism’s lifetime.

Darwinism: Random variations within a population due to mutation, gene recombination, etc.

Question 3

A4.1.2—Evidence for evolution from base sequences in DNA or RNA and amino acid sequences in proteins

Answer 3

At the most basic level, all living organism share:
The same genetic material (DNA)
The same, or highly similar genetic codes
The same basic process of gene expression (transcription and translation)
These similarities indicate that all living things are descended from a common ancestor

Question 4

NOTE: Since the theory of evolution states that all species arose from one ancient common ancestor, DNA, RNA, and amino acid bases can be sequenced and analyzed in order to make comparisons between species. The more similar the sequences of two species are, the more likely that they recently branched off from a common ancestor.

Question 5

A4.1.3: Evidence for evolution from selective breeding of domesticated animals and crop plants

Define selective breeding and artificial selection.

why evidence for evolution?

Answer 5

• Selective breeding is a form of artificial selection, whereby man intervenes in the breeding of species to produce desired traits in offspring. By breeding members of a species with a desired trait, the trait’s frequency becomes more common in successive generations.
• Artificial selection = selective breeding that is imposed by an external entity, usually humans, in order to enhance the frequency of desirable features.

Question 6

List reasons why humans have selectively bred domesticated animals and crop plants.

Answer 6

• Selective breeding of plant crops has allowed for the generation of new types of foods from the same ancestral plant source
• Selective breeding of domesticated animals has also resulted in the generation of diverse breeds of offspring
• better quality/better yield/diseases resistance/can do…/animals that can’t cause harm (w/out horns)

Question 7

• Outline how selective breeding can lead to rapid evolutionary change.

Answer 7

• Selective breeding leads to faster change than natural selection; this is because only the selected individuals are allowed to breed together, while in natural selection there will still be some breeding between individuals with less favourable alleles
• The next gen, will have an increased frequency of the desired allele and this process will continue until the entire generation has the desired trait.

Question 8

Explain an example of artificial selection in a crop plant.
Explain an example of artificial selection in a domestic animal.

Answer 8

• Plants of the genus Brassica have been bred to produce different foods by modifying plant sections through artificial selection. This includes broccoli (modified flower buds), cabbage (modified leaf buds) and kale (modified leaves)
• Cows have been selectively bred across many generations to produce offspring with improved milk production
  Farmers have also targeted the breeding a cows with a mutation resulting in increased muscle mass. The resulting stock of cattle (termed Belgian Blue) have excessive bulk and produce more edible lean meat

Question 9

A4.1.4—Evidence for evolution from homologous structures

Define and state an example of homologous structures.
Define pentadactyl limb.
List the bone structures present in the pentadactyl limb.
Identify pentadactyl limb structures in diagrams of amphibians, reptiles, birds and mammals.
Relate differences in pentadactyl limb structures to differences in limb function.

Define vestigial structure.
State an example of a vestigial structure.

Answer 9

• Homologous structures are those that are similar in shape/same ancestors, but have different function
  EX: A dolphin fin and bat wing - both pentadactyl limbs

-Vestigial structure = features that no longer serve the function they do in similar species (remnants of structures in an ancestral species that had a use for them)
EX: appendix and wisdom teeth

• Pentadactyl limb = a limb with 5 digits; includes humerus/femur, radius and ulna/tibia and fibula/carpals and tarsals, phalanges &meta c.&t.

Question 10

A4.1.5: Convergent evolution as the origin of analogous structures
Define analogous structure.
State an example of an analogous structure found in two species.
Outline how convergent evolution results in analogous structures.

Answer 10

• Analogous structure = structures with similar functions, but different shapes and different origins
• EX: Wings of bats and birds
• Convergent evolution occurs when different species evolve similar biological adaptations in response to similar selective pressures. This happens when species occupy similar ecological niches.

Question 11

divergent evolution

Answer 11

occurs when an ancestral species splits into two reproductively isolated groups, causing each group to develop different due to their respective selective pressures and natural selection.

Question 12

A4.1.6: Speciation by splitting of pre-existing species
- Define speciation.
- Compare the process of speciation with that of gradual evolutionary change in an existing species.
- State the impact of speciation and extinction on the total number of species on Earth.

Answer 12

• Speciation = the evolutionary process by which new species form, where one species is split into two or more species
• Gradual evolutionary change: no barrier required/definitions/not creating another species
• Speciation: there must be a barrier for gene flow/definitions/literally creating another species!
• both require natural selection as a mechanism of change
• If the rate of speciation is higher than the rate of extinction, the number of species present will grow, and conversely, if extinction rate is higher, the number of species present will fall.

Question 13

A4.1.7: Roles of reproductive isolation and differential selection in speciation
- Define reproductive isolation.
- Outline how reproductive isolation and differential survival (adaptations) lead to speciation.

Answer 13

• Reproductive isolation = occurs when changes in the alleles and phenotypes of some individuals in a species prevent them from successfully breeding with other individuals that don’t have these changed alleles or phenotypes
• unable to merge genetic material geographical, behavioral, physiological, or genetic differences./different environment, different selection

Question 14

• Outline examples of speciation.
• Explain how reproductive isolation can maintain the divergent evolution of two separate species occupying the same habitat.

Answer 14

• The lava lizards of the Galápagos Islands are an example of this. One species is present on all the main islands of the archipelago. On six smaller islands there is a closely related but different species, formed by migration to the island and by reproductive isolation and divergence due to differential
  selection.
• CAN’T SWAP GENETIC MATERIAL