TOPIC 5 - Evolution

Question 1

2 things needed for nat sel

Answer 1

variation (mutation, meiosis or sexual reproduction)
competition

Question 2

What are acquired characteristics? Are they needed for evolution to occur?

Answer 2

An acquired characteristic is a non-heritable change in the structure or function of an organism by disease, injury, deliberate modification, repeated use, disuse or other environmental influences. They are not passed on to offspring through reproduction alone and therefore not required for evolution.

Question 3

What is gradual divergence?Give an example or describe how it occurs.

Answer 3

When separate populations of the same species adapt to the conditions available to them. Some genes are selected for, some no, depending on the selective pressures of the environment. These pressures produce differences in the populations over time, becoming so great that the two populations are no longer the same species. Ex: pollen from north species of marsh grass pollinating flowers from south species, producing infertile offspring, means speciation by gradual divergence has occurred.

Question 4

What is adaptive radiation? Give an example

Answer 4

Adaptive radiation is the rapid diversification of new species from an ancestral source, each species adapted for a specific unoccupied niche. For example, speciation of hawaiian honeycreepers occured

Question 5

Species definition

Answer 5

A group of interbreeding populations with a common gene pool that are reproductively isolated from other groups

Question 6

Speciation definition

Answer 6

Occurs at the population level. Populations of one species may evolve to become different species.

Question 7

Highlight the phylum which lacks xylem and phloem tissue

Answer 7

Bryophytes

Question 8

Highlight the phylum which contains vertebrates.

Answer 8

Chrodata have a notochord at some point in their development (a line of supporting cartilage) - Mammals, fish, reptiles, amphibians, birds

Question 9

Describe evidence scientists use to identify members of a clade.

Answer 9

Morphological evidence (looking for analogous traits)
Molecular evidence (looking for similarities of base sequences of a gene and amino acid sequences in a protein) The number of differences between base sequences demonstrates the degree of evolutionary divergence. Time of divergence can be used if gene sequences mutate at a constant rate

Question 10

What is a clade

Answer 10

A group of organisms evolved from a common ancestor

Question 11

What things can cause variation in a population?

Answer 11

Changes to allele frequency can result from genetic mutation (mutation causes change in base sequence), sexual reproduction (new gene combinations) and genetic drift (Genetic drift is the change in the composition of a gene pool as a result of chance or random events)

Question 12

Explain why variation is important when talking about evolution due to natural selection.

Answer 12

know this

Question 13

Founder effect

Answer 13

When a small group breaks away with varying gene frequency, more subject to genetic drift

Question 14

What is natural classification and why is it such a useful system?

Answer 14

Natural classification groups species that share a common ancestor. Useful to determine how closely related species are, showing evolutionary links and predicting characteristics shared by members of a group. A disadvantage of natural classifications is that because they predict evolutionary relationships, they change with new information about species that scientists are constantly discovering

Question 15

What unique features distinguish mammals from other classes of vertebrates?

Answer 15

Hair/fur on body
Have mammary glands that secrete milk to feed young
Have lungs with alveoli

Question 16

Explain temporal isolation

Answer 16

Temporal isolation occurs when two populations differ in their periods of activity or reproductive cycles, therefore preventing them from mating and interbreeding to produce fertile offspring. For example: Leopard frogs and wood frogs reach sexual maturity at different times in the spring and hence cannot interbreed

Question 17

Explain behavioural isolation

Answer 17

The lifestyle and habitats of two species are incompatible, preventing them from mating. For example: certain populations of crickets may be morphologically identical but only respond to specific mating songs

Question 18

Explain geographic isolation

Answer 18

Physical barriers preventing species from mating, like lakes, rivers, etc. For example: Lions and tigers occupy different habitats and do not interbreed (usually)

Question 19

What is reproductive isolation

Answer 19

Reproductive isolation occurs when barriers prevent two populations from interbreeding – keeping their gene pools separate

Question 20

How does reproduction isolation lead to speciation?

Answer 20

Two populations cannot mate anymore to produce offspring.

Question 21

Explain directional selectrion

Answer 21

When one phenotype extreme is favoured at the expense of the other. The favoured phenotype is more likely to survive and produce offspring, so organisms with the selected for alleles become more frequent (the allele frequency of the population changes). Graph: Dotted line to left/right.

Question 22

Explain stabilizing selection

Answer 22

The intermediate phenotype is favoured over two extremes, therefore organisms with interm phenotype will reproduce, frequency of alleles changes, selection occurs, etc. Graph: dotted lines outside. An example of stabilising selection is human birth weights (too large = birthing complications ; too small = risk of infant mortality)

Question 23

Disruptive selection

Answer 23

Extremes favoured over intermediate. Phenotypic distribution deviates from intermediate. This occurs when fluctuating environmental conditions (e.g. seasons) favour the presence of two different phenotypes. Example: proliferation of black or white moths in regions of sharply contrasting colour extremes

Question 24

Distinguish between homologous and analogous structures. What do they tell you about organisms’ evolutionary history and relationships?

Answer 24

Homologous structures shared structures that come from a common ancestor, have similar morphological structure but may have different function (pentadactyl limb used for mibility) Analogous structure does not come from a common ancestor but is still a shared characteristic.

Question 25

What can be a difficulty of using a cladogram to gather data about ancestry of different species?

Answer 25

Grouping by morphological evidence. Can have similar structures but not come from common ancestor.
Extinct species makes it difficult to study evolutionary relationships