Unit 3

Question 1

xwhat are the 5 sources of evidence of evolution

Answer 1

1. Fossil record
2. Biogeography
3. Anatomy
4. Embryology
5. DNA

Question 2

1. Evidence from the fossil record

Answer 2

provides evidence
- fossils closer to the surface are more similar to species that are alive today compared to those deeper
- fossils appear in chronological order in rock layers
TRANSITIONAL FOSSILS: show intermediary links between groups of organisms
- this helps scientists better understand evolution and relationships between organisms
- transitional fossils link the past with the present

Question 3

2. Evidence from Biogeography

Answer 3

• study of the past and present geographical distribution of organisms
• geographically close environments are likely to be populated by related species than similar environments that are separate

Question 4

Evidence from Anatomy

Answer 4

• vertebrate forelimbs can be used for flying, running, and swimming
• although they have different functions, they all have the same set of bones all organized similarly
• the basic vertebrate forelimb originating from a common ancestor is plausible

-homologous structures: structures with similar structural elements and origin but may have different functions

Analogous structures: body parts that perform similar functions, not evolved from the same ancestors
- structural composition is normally very different

Question 5

4. Evidence from Embryology

Answer 5

study of early pre-birth stages of the development of an organism
- it can be used to determine evolutionary relationships between animals
- the embryos of different organisms exhibit similar stages of embryonic development

Question 6

Evidence from DNA

Answer 6

• evolutionary relationships between species can be found in DNA since it carries genetic information
• 2 species have similar patterns in the DNA which can indicate they are from the same ancestors

Question 7

Adaptations

Answer 7

make organisms ideal for their habitat
- structural behavior or physiological process that helps an organism survive and reproduce in a particular environment

Question 8

Examples of Adaptations

Answer 8

Hibernation: physiological adaptation
- allows organisms to survive harsh climates

Migration: behavioural adaptation
- seasonal or annual migration changes the habitat of animals
- maximizes breeding and feeding potential

Camouflage: structural adaptation

Question 9

Variation

Answer 9

structural, functional, or physiological differences between individuals
- not all variations become adaptations
–> determined by environmental factors for it to be positive, negative, or no effect

Question 10

Explain how mutations might lead to genetic variation

Answer 10

mutations: changes in genetic material of an organism
- mutations such as ultraviolet radiation, are environmental agents that can also cause mutations in DNA

Question 11

Selective advantage

Answer 11

• genetic advantage of one organism over its competitors
• over time it causes the organisms to be favoured in survival and reproduction in changing environmental conditions

Question 12

natural selection?

Answer 12

the process that results when the characteristics of a population of organisms change over many generations
- very situational: some times can have no impact but others can help individuals survive and reproduce

Question 13

selective pressure?

Answer 13

abiotic environmental conditions select for certain characteristics while. it selects against others

Question 14

fitness

Answer 14

the contribution an individual makes to the gene pool of the next generation by producing offspring that survive long enough to reproduce

high fitness = surviving and reproduce
low fitness = low/no viable offspring

Question 15

sexual selection

Answer 15

natural selection for mating based on competition between males or through displays and choices made by females

Question 16

types of natural selection

Answer 16

1. stabilizing selection
   - favours an intermediate phenotype
   - acts againsed extreme varients of the phenotype
   - most common phenotype is made more common in the population
   - extreme forms of the phenotype are removed
   - occurs when environment conditions are constant

2.Directional Selection
- favours phentypes at one extreme
- common during times of envionrmental change
- when a population migrates to a new habitat that have differnet enviornmental conditions

3. Distributive selection
   - also called diversifying selection
   - when extremes of range of phenotypes are favoured over intermediate ones
   - intermediate phenotypes cna be eliminated from the population

Question 17

artificial selection

Answer 17

• selective pressure exerted by humans on populations in over to improve or modify particular desirable traits
• eg: selective breeding
  natural selection: due to enviornment
  artificial selection: due to humans

Question 18

what are some consequences of artificial selection?

Answer 18

• genetic engineering introduces new genetic information into domesticated organisms
• reduces genetic diversity because the main goal of domesticating organisms is to produce similar ones
• artificially selected crops normally have increased nutritional value and less pests
• plants bred to grow cannot tolerate bad soil conditions
• in animals it can cause problems in respiratory system

Question 19

allele frequencies

Answer 19

the number of copies of an allele compared to the total number of alleles in a population

Question 20

factors that change allele frequencies in population

Answer 20

5 factors that lead to evolutionary changes
- mutation
- gene flow
- non-random mating
- genetic drift
- natural selection

Question 21

mutations

Answer 21

• mutation randomly introduces new alleles into a population
• change in DNA of an individual
• can effect the entire gene pool
• ## the greater diversity, the greater chance for selective advantage for some individuals

Question 22

gene flow

Answer 22

• occurs between 2 different interbreeding populations that have different allele frequencies
• it is the net movement of alleles from one population to another as a result of migration of individuals
• population A to population B

Question 23

non-random mating

Answer 23

• interbreeding
• when closely related indivudals breed together
• homozygous genotype frequencies are increased since close relatives share similar genotypes
• can lead to harmful recessive alleles being expressed (deformities and health problems)

Question 24

genetic drift

Answer 24

• random change in genetic variation from generation to generation due to chance
• the smaller the population, the less likely the parent gene pool will be reflected in the next generation compared to a larger population

Question 25

2 situations that lead to significant genetic drift

Answer 25

1. the founder effect
   - a change in gene pool that occurs when a few individuals start a new isolated population
   - few individuals form a new population
2. population bottleneck
   - change in gene distribution that results from a decrease in population size
   - (starvation, disease, human activities, natural disasters)
   - survivors only have a fraction of alleles before so the gene pool will loose diversity quickly.

Question 26

speciation

Answer 26

formation of new species from existing species
- when new species are formed and seen it is called macroevolution

• when members of a sexually producing population can change so much that they can no longer produce viable offspring with original population

Question 27

pre-zygotic isolating mechanisms

Answer 27

• impedes mating between species or prevent fertilization of the eggs if individuals from different species attempt to mate
  5 types:
  (prevention of mating)
  1. behavioural isolating mechanisms
• any special signals or behaviours specific to the species that prevent interbreeding
  (songs of birds)

2. Habitat Isolating Methods
   - 2 species living in the same region but different habitats so they don’t encounter each other
3. temporal isolating mechanism
   - same habitat but different mating or flowering times
   (different times of day/seasons/years)

(prevention of fertilization)
4. mechanical isolating mechanisms
- anatomically incompatible (fail to fertilize)
- different species genitals will not fit together

5. gametic isolating mechanisms
   - the sperm in one species will not fertilize
   - rarely form a zygote

Question 28

post-zygotic isolating mechanisms

Answer 28

rare occasions when the two species can successfully fertilize –> there are barriers that prevent the hybrid zygotes from developing into a viable and fertile offspring

• 3 types:
  1. hybrid inviability:
• genetic incompatibility of the species maybe stop developing the hybrid zygote
• prevents normal mitosis

2. hybrid sterility (infertility)
   - two species can sometimes mate and produce hybrid offspring
   - offspring cannot further reproduce after that
3. hybrid breakdown (morality)
   - sometimes the first generation of hybrids are fertile but not of the second generation

Question 29

types of speciation

Answer 29

1. sympatric speciation
   - speciation in which populations within the same areas diverge and become reproductively isolated
2. allopatric speciation
   - population is split into 2 or more isolated groups by a geographical barrier
3. adaptive radiation
   - the diversification of a common ancestral species into a variety of differently adapted species
4. divergent evolution
   - species that were once similar to an ancestral species diverge or become extremely different
5. convergent evolution
   - similar traits arise because different species have independently adapted to similar environmental conditions