Unit 5 - Ch 18, 20 - Evolution

Question 1

Evolution

Answer 1

How organisms adapt to the environment over time

Question 2

Microevolution

Answer 2

Small scale changes. Changes in gene frequencies within populations. Not disputed in the scientific community.

Question 3

Macroevolution

Answer 3

One group giving rise to another. Large shifts occur in the morphology and / or physiology. Disputed in the scientific community.

Question 4

Darwin’s Premises (4)

Answer 4

1. Excess Reproduction
2. Variation/Inheritance
3. Survival of Fittest - i.e. Natural Selection.
4. Gradual Change - i.e. Gradualism.

Question 5

Excess Reproduction

Answer 5

Darwin’s premise.

Far more offspring are born than can survive to become adults. Malthus

Question 6

Variation / Inheritance

Answer 6

Darwin’s premise.

Observed in breeding of animals and plants. Also Lamark’s Theory of Acquired Characteristics.

Question 7

Survival of Fittest - i.e. Natural Selection

Answer 7

Darwin’s premise

The best adapted offspring survive and reproduce. Wallace originally published this idea in 1858.

Question 8

Gradual Change

Answer 8

Darwin’s premise

Species change gradually over time. Lyell was the founder of uniformitarianism which replaced catastrophism.

Question 9

Sources of Variation (2)

Answer 9

1. Sexual Reproduction - Reshuffles existing genetic information through crossing over (prophase I), independent assortment (Metaphase I), and fertilization.
2. Mutation - The only source for “new” genetic information for natural selection to operate on. Occurs randomly so usually harmful.

Question 10

Evidence of Natural Selection (2)

Answer 10

1. Industrial Melanism (Kettlewell) - Biston betularia (peppered moth). During the industrial revolution.
   a. 1850 - 99% light/1% dark
   1900 - 10% light/90% dark
2. Resistance - Induced Evolution (by humans)
   a. Antibiotic/Pesticide Resistance

Question 11

3 types of natural selection

Answer 11

1. Stabilizing Selection
2. Directional Selection
3. Disruptive Selection

Question 12

Stabilizing Selection

Answer 12

The average phenotype is maintained. Extreme variants are eliminated. Beneficial in environments that are stable.

a. Clutch Size (starlings) - number of eggs per nest
b. Albino deer - easier for hunters to spot

Question 13

Directional Selection

Answer 13

One extreme phenotype is favored over the average - occurs when the environment is changing

a. Disease resistant oysters

Question 14

Disruptive Selection

Answer 14

Extreme phenotypes become favored over the average in different environments in different parts of the range - may lead to speciation.

Question 15

Species definition

Answer 15

A group of morphologically similar individuals capable of interbreeding and reproductively isolated from other species.

Question 16

Isolating Mechanisms (how separation occurs in gene pools) premating and postmating

Answer 16

1. Premating
   a. Habitat
   b. Temporal
   c. Behavioral
   d. Mechanical
2. Postmating
   a. Gamete Mortality
   b. Zygote Mortality
   c. Hybrid Sterility
   d. Depressed F2 Fitness

Question 17

Habitat as an isolating mechanism

Answer 17

Occurs premating

Species utilize different micro environments so they rarely encounter one another

Question 18

Temporal isolation mechanism

Answer 18

Occurs Pre-mating

Timing of reproduction is different between species. Common in plants: pollen release and stigma receptivity to pollen.

Question 19

Behavioral isolating mechanisms

Answer 19

Species have specific mating rituals or courtship displays. Fire flies.

Occurs premating

Question 20

Mechanical isolating mechanisms

Answer 20

Reproductive systems are unsuitable for copulation

Occurs premating

Question 21

Gamete mortality isolating mechanisms

Answer 21

Gametes are not capable of fertilizing gametes of other species. Common in organisms that use external fertilizers like fish and sea urchin.

Occurs postmating

Question 22

Example of a zygote mortality isolating mechanism

Answer 22

Sheep and goat hybrids form but are usually stillborn.

Occurs post mating

Question 23

Hybrid sterility isolation mechanisms

Answer 23

The resulting hybrid is sterile. Mules for example: a 2n=64 Horse breeds with a 2n=62 Donkey resulting in a sterile Mule.

Question 24

Depressed F2 Fitness

Answer 24

This is where we see hybrid vigor in early generations, but eventually die off occurs in future generations.

Post mating isolation mechanism

Question 25

Speciation

Answer 25

One species giving rise to another.

Restricted gene flow must occur
- Populations becomes reproductively isolated from each other and create separate gene pools.

Question 26

Allopatric speciation

Answer 26

These have geographic separation between populations. The separation can be relatively small depending in the species’ capabilities to travel.

Question 27

Sympatric speciation

Answer 27

Polyploids become reproductively isolated from others in the same location. This is common in plants: eventually a 4n plant will isolate from a 2n plant.

Question 28

Patterns of Evolution (3)

Answer 28

Convergent evolution

Divergent evolution

Coevolution

Question 29

Convergent evolution
Structure?
Environment?

Answer 29

(coming together)
Unrelated species demonstrate similar adaptations to their environment

1. Analagous structures
   - Structurally diverse but functionally similar => wings (birds, bats, insects)
2. Similar environments
   - similar selection pressure for similar adaptations

Question 30

Divergent evolution
Structure?
Environment?

Answer 30

(moving apart)
Related species demonstrate different adaptations to their environment. Suggests common ancestry.

1. Homologous structures
   - Have structural similarity, but functional diversity. => arm structure in terrestrial mammals and whales.
2. Different environments
   - Different selection pressure

Question 31

Coevolution

Answer 31

AKA Parallel Evolution
Symbiotic / Mutualistic
Unrelated species with adaptations that are utilized for the survival of both

=> the yucca moth is the only known pollinator of the yucca plant, and the plant is the only known area where the moth completes its life cycle.