Chapter 5 (10.3)

Question 1

What are homologous structures?

Answer 1

Similar structured organs or bones that can demonstrate decent from a common ancestor amongst different species

Question 2

What is adaptive radiation?

Answer 2

The rapid evolution of diversely adapted species from a common ancestor upon introduction to new environmental opportunities

Question 3

Give two examples of homologous structures (that we have covered) that have evolved by adaptive radiation.

Answer 3

The pentadactyl limb in vertebrae’s is a homologous structure that adapted to different mode of locomotion in particular environments

Question 4

Describe the development of melanistic insects in polluted areas

Answer 4

Normal environment: in an unpolluted area trees were pale in colour, allowing for moths to camouflage to avoid predators
Selective pressure: predation from birds whilst resting
Environmental change: pollution blackened the tree branches
Result: dark moths were better camouflaged from birds and survived to reproduce. Light moths were easily spotted and only few survived to reproduce
Evolution: over generations, the dark moths have increased with frequency and the heritable characteristic of the population have changed.

Question 5

Explain the theory of evolution by natural selection.

Answer 5

Organisms that are better adapted to their environment are more likely to survive and pass on the genes that aided their success

Question 6

What are the 5 steps of evolution by natural selection?

Answer 6

1) Overproduction: species produce more young than will survive
2) There is a selective pressure: competition for resources, or a change in environment or a predator..
3) Variation: individuals vary from one another in many characteristics. The variation is inherited
4) Survival of the fittest phenotype: the individuals with the most favourable characteristics will be most likely to survive and pass their genes
5) Favourable characteristics increase: each new generation will contain more offspring from individuals with favourable characters than those with unfavourable ones, changing the population over time.

Question 7

What are antibiotics?

Answer 7

Antibiotics are medications that kill or inhibit the growth of bacteria

Question 8

Describe the process of antibiotic resistance in bacteria.

Answer 8

• The overuse of antibiotics can lead to the production of resistant strains of bacteria.
• A mutation may code for an ability to inactivate the antibiotic
• a mutant gene may code for an ability to alter the target of the antibiotic
• a mutation may alter the permeability of the bacterial cell to the antibiotic.
• a plasmid containing antibiotic resistance is transferred via a sex pilus between the bacteria during the process of conjugation

Question 9

What is binomial nonmenclature?

Answer 9

The system on naming organisms using two names

Question 10

How do genus and species names indicate how closely related species are?

Answer 10

• The genus and higher taxa consist of species that have evolved from one common ancestral species.
• A genus can be established when genetic similarities are found, all members of this genus (the species group) evolved from a common ancestor.

Question 11

What is reclassification? Why are organisms reclassified?

Answer 11

• Reclassifying organisms based on modern techniques of classification (eg. using ribosomal RNA).
• The past Classification of organisms was based on observable characteristics rather than DNA.
• (and)organisms were put into the same genus despite not being closely related.

Question 12

What is a dichotomous key? Know how to construct one.

Answer 12

A dichotomous key is a method of identification whereby groups of organisms are divided into two categories repeatedly.

Question 13

What is a clade?

Answer 13

A group of organisms that have evolved from a common ancestor

Question 14

Describe the difference between analogous and homologous features.

Answer 14

Homologous structures are similar cause of common ancestry. Analogous structures are similar because of convergent evolution.

Question 15

How can biochemical evidence be used to support the idea of a common ancestor?

Answer 15

• Biochemical evidence (including DNA and protein structures) has confirmed the idea of a common ancestor.
• All living organisms on Earth use DNA which is evidence that all life on Earth has a common ancestor

Question 16

What is a gene pool?

Answer 16

All the genes and their different alleles present in an interbreeding population

Question 17

What does allele frequency refer to?

Answer 17

Is a measure of the proportion of specific variation of a gene in a population

Question 18

What causes variation in a gene pool? How does this lead to evolution?

Answer 18

• New alleles can be introduced through mutations;
• Some alleles are more successful and better adapted than others, leading to evolution.
• Gene pools may also change due to immigration and emigration (=variation)
• Populations may gain or lose allele frequency through gene flow
• Genetic drift and non-random mating also contributes to variation.

Question 19

What is a species? What are contradictions to the definition?

Answer 19

• species are groups of potentially or actually interbreeding natural populations, with a common gene pool, which are reproductively isolated from other such groups
• Contradictions: species that reproduce asexually; members do not interbreed, extinct species because it can’t be inferred whether species interbred.

Question 20

What is speciation? What is the difference between sympatric and allopatric speciation? Examples?

Answer 20

• Speciation is a linage-splitting event that produces two or more separate species from a single common ancestor.
• Sympatric speciation occurs when two varieties of a species live in the same geographical area, but do not interbreed (eg. Temporal isolation (eastern spotted skunk & western spotted skunk)).
• Allopatric is more common and occurs when members of a species migrate to a new area, forming a population that is geographically isolated from the rest of the species (eg. Geographic isolation (physical barriers preventing males and females from mating)).

Question 21

What is punctuated equilibrium?

Answer 21

Quick changes followed by long periods of little to no change. “Long periods of relative stability in a species are punctuated by periods of rapid evolution”

Question 22

What is reproductive isolation? How can it occur? How does it lead to evolution?

Answer 22

Barriers preventing populations of members of the same species from interacting and reproducing
- Geographic isolation
- Temporal isolation
- Behavioural isolation
- Issues relating to infertility cause by hybridisation