Lecture 4: Evolution and Ecology

Question 1

Biology all arises from

Answer 1

process of evolution

Question 2

Evolution

Answer 2

change in allele frequency in population over time

Question 3

Gene

Answer 3

basic physical and functional unit of heredity (DNA), specify how to build proteins

Question 4

Allele

Answer 4

variant or specific form of a gene

Question 5

Phenotype

Answer 5

observable characteristics of an organism
Ex. size or color

Question 6

Fitness

Answer 6

organism’s ability to survive and reproduce within its environment

Question 7

Frequency

Answer 7

relative abundance of an allele in a population or another unit which evolution is being examined

Question 8

4 mechanisms of evolution

Answer 8

1. mutation
2. natural selection
3. genetic drift
4. gene flow

Question 9

_____ evolve, not ______!

Answer 9

Populations ; individual

Question 10

Mutation

Answer 10

random introduction of a new allele
rare
usually disadvantageous and dies out
necessary for variability –> provides raw material for evolution

Question 11

3 types of natural selection

Answer 11

Directional, stabilizing, disruptive

Question 12

Requirements for natural selection

Answer 12

• population has variation
• differences are genetic (heritable)
• differences influence (individual fitness)

Question 13

Natural selection

Answer 13

Darwin’s survival of the fittest
When individuals with particular heritable traits consistently leave more offspring than do individuals with other heritable traits
MAIN MECHANISM OF ADAPTIVE EVOLUTION

Question 14

Disruptive selection:

Answer 14

favorable to both extremes and no intermediate
can cause speciation

Question 15

What is the main and only mechanism for adaptive evolution?

Answer 15

Natural selection

Question 16

Directional selection:

Answer 16

favorable to one extreme

Question 17

Genetic drift

Answer 17

Occurs when chance events determine which alleles are passed to the next generation
Drift is always occurring
Can overwhelm selection
Causes many differences between isolated populations

Question 18

How can genetic drift overwhelm selection?

Answer 18

Favorable mutations usually starting from rarity may be lost due to drift despite benefits
Can cause unfavorable alleles go to fixation

Question 19

Stabilizing selection:

Answer 19

favorable to middle/ mean

Question 20

Why is genetic drift important in small populations?

Answer 20

allele frequencies fluctuate at random
genetic variation of population is reduced
frequency of harmful alleles can increase if they only have mildly deleterious effects
chance events may lead to allele fixation in one population and loss from another population

Question 21

Gene Flow

Answer 21

Caused by immigration and emigration
From populations with differing allele frequencies
Can limit local adaptation causing homogenization

Question 22

Adaptive evolution

Answer 22

traits that confer survival or reproductive advantage that tends to increase in frequency over time
can be quite fast

Question 23

Ingredients needed for Adaptive evolution:

Answer 23

variability in population
heritability of that variability
differential fitness

Question 24

Adaptations are not perfect due to

Answer 24

environment not static
emigration, immigration
drift and mutation

Question 25

Evolutionary Constraints

Answer 25

1. Lack of generation
2. Evolutionary history
3. Ecological tradeoffs

Question 26

How is lack of generation an evolutionary constraint?

Answer 26

If there is no beneficial allele, adaptive evolution at that gene cannot occur
Advantageous alleles arise by chance, not on demand

Question 27

How is evolutionary history an evolutionary constraint?

Answer 27

Natural selection works on traits that already exist
Organisms have certain characteristics and lack others because of their ancestry
To evolve, each small step generally needs to be beneficial itself
Ex. Dolphins evolved from terrestrial mammals; they have lungs and cannot breathe underwater

Question 28

How is ecological an evolutionary constraint?

Answer 28

Organisms do many things over their lives
Traits that would make them better at one thing might make them worse at another
Ex. Duck Feet help them swim, but not walk

Question 29

Evolution and Ecology can do feedback to each other

Answer 29

Constant cycle of change in environment –> change in which traits are beneficial in the environment –> change in population and community –> back to change in the environment

Question 30

Speciation

Answer 30

Can be caused from disruptive selection
Occurs when populations have accumulated enough differences to stop gene flow
Once reproductive barriers are in place local adaptation can proceed more effectively and create daughter species
Difficult to kick off in the first place

Question 31

The key to speciation is development of

Answer 31

reproductive barriers –> cease gene flow across populations

Question 32

Reproductive barriers can be:

Answer 32

behavioral or biological

Question 33

Diversity

Answer 33

function of speciation and extinction

Question 34

How many mass extinction events?

Answer 34

5

Question 35

Diversity is driven by

Answer 35

major environmental changes

Question 36

Adaptive radiation is a major speciation event that is

Answer 36

group of organisms gives rise to many new species that expand into new habitat or fill new ecological roles

Question 37

Diversity shows interdependency of ecology by

Answer 37

When some species go, many others follow
Creates huge chances on Earth

Question 38

What are ways human actions alter the course of evolution?

Answer 38

Pollution
Habitat fragmentation
Overharvesting
Introductions of invasive species

Question 39

Human actions can alter mechanisms of evolutions

Answer 39

natural selection, genetic drift, gene flow

Not mutation!

Question 40

Extinction rate today is ___ to ____ higher

Answer 40

100 to 1000

Question 41

What will become leading cause of extinctions in coming decades?

Answer 41

Climate change