Evolution

Question 1

Natural Selection

Answer 1

• “survival of the fittest”
• theory that certain characteristics or traits possessed by individuals within a species may help those individuals to have greater reproductive success and pass those trait to offspring
• mechanism for evolution, not the same thing as evolution
• the history of differential selection over time
• does not occur in populations that do not have any genetic diversity – if entire population is homozygous at one loci then natural selection will not act on this gene

Question 2

What are the 3 basic tenets that built the theory of natural selection?

Answer 2

• organisms produce offspring, few of which survive to reproductive
• chance variations that give an organism a slight survival advantage are considered favorable variations
• individuals with a greater preponderance of these favorable variations are more likely to survive to reproductive age and produce offspring; this level of reproductive success is termed fitness

Question 3

neo-Darwinism

Answer 3

• modern synthesis model of natural selection
• adds knowledge of genetic inheritance and changes in the gene pool to Darwin’s original theory
• includes terms such as differential reproduction, inclusive fitness, and punctuated equilibrium

Question 4

Differential Reproduction

Answer 4

• when mutation or recombination results in a change that is favorable to the organism’s reproductive success, that change is more likely to pass on to the next generation (the opposite is true too)
• individuals with more viable offspring are selected for and individuals who produce less viable offspring are selected against

Question 5

Because it is the gene pool that changes over time, it is _____ that evolve, not ____

Answer 5

• populations

- individuals

Question 6

Inclusive Fitness

Answer 6

• a measure of an organism’s success in the population
• based on the number of offspring, success in supporting offspring, and the ability of the offspring to then support others
• promotes the idea that altruistic behavior can improve the fitness and success of a species as a whole (new concept for modern theories of natural selection and is not found in Darwin’s theory)

Question 7

Punctuated Equilibrium

Answer 7

• suggests that changes in some species occur in rapid bursts rather than evenly over time
• occurs when little evolution happens within a lineage of related lifeforms for long periods of time, followed by a massive explosion of evolutionary change

Question 8

What are the 3 different modes of natural selection?

Answer 8

• stabilizing selection
• directional selection
• disruptive selection

Question 9

Stabilizing Selection

Answer 9

• keeps phenotypes within a specific range by selecting against extremes
• intermediate phenotypes are more fit than extreme ones
• Ex. human birth weight is maintained within a narrow band by this type of selection

Question 10

Directional Selection

Answer 10

• created by adapted pressure
• leads to the emergence and dominance of an extreme phenotype
• occurs when a new standard phenotype emerges as a result of differential survivorship
• Ex. heterogenous plate of bacteria that is treated with antibiotics and only those colonies that exhibit resistance to the antibiotic survive

Question 11

Disruptive Selection

Answer 11

• two extreme phenotypes are selected over the norm
• extremes are more fit than those in the middle
• facilitated by polymorphisms
• Ex. finches on the Galapagos Islands only exhibited large or small beaks, none had a medium sized beak

Question 12

Polymorphisms

Answer 12

naturally occurring differences in form between members of the same population, such as light and dark coloration in the same species of butterfly, or hair color

Question 13

Adaptive Radiation

Answer 13

• describes the rapid rise of a number of different species from a common ancestor
• benefit of this is that it allows for various species to occupy different niches
• favored by environmental changes or isolation of small groups of the ancestral species
• this could occur (speciation) if one species was placed in several different environments

Question 14

Niche

Answer 14

-a specific environment, (including habitat, available resources, and predators) for which a species can be specifically adapted

Question 15

Species

Answer 15

the largest group of organisms capable of breeding to form fertile offspring

Question 16

Speciation

Answer 16

• the formation of a new species
• this can occur due to barriers that prevent successful interbreeding within a species
• can also occur through evolution

Question 17

What are the two ways reproductive isolation can occur?

Answer 17

• prezygotic mechanisms

- postzygotic mechanisms

Question 18

Prezygotic Mechanisms

Answer 18

• prevent formation of a zygote completely
• examples: temporal isolation (breeding at different times), ecological isolation (living in different niches with the same territory), behavioral isolation (lack of attraction between members of the two species due to differences in pheromones, courtship displays, etc), reproductive isolation (incompatibility of reproductive anatomy), or gametic isolation (intercourse can occur but fertilization cannot)

Question 19

Postzygotic Mechanisms

Answer 19

• allow for gamete fusion but yield either nonviable or sterile offspring
• examples: hybrid inviability (formation of a zygote that cannot develop to term), hybrid sterility (forming hybrid offspring that cannot reproduce), and hybrid breakdown (forming first-generation hybrid offspring that are viable and fertile but second-generation offspring are inviable or infertile)

Question 20

What are the three patterns of evolution that can be seen when analyzing a species?

Answer 20

• divergent evolution
• parallel evolution
• convergent evolution

Question 21

Divergent Evolution

Answer 21

• independent development of dissimilar characteristics in two or more lineages sharing a common ancestor
• Ex. seals and cats (or bats and horses) are both mammals in the order Carnivora yet they are very different in general appearance

Question 22

Parallel Evolution

Answer 22

• the process whereby related species evolve in similar ways but through different mechanisms for a long period of time in response to analogous environmental selection pressures
• same lineage
• Ex. feeding structure of crustaceans – came from a mutation in a pair of legs and turned them into mouth parts (lobsters, crabs, and shrimp have a common ancestor but are all different species that have similar mouth structures)

Question 23

Convergent Evolution

Answer 23

• the independent development of similar characteristics in two or more lineages not sharing a recent common ancestor
• different lineage with similar environments
• Ex. fish and dolphins (or sharks and dolphins) have come to resemble one another physically although they belong to different classes of vertebrates

Question 24

Fitness

Answer 24

• ability to pass on genetic material through reproduction
• Ex. someone that is strong/healthy/long-lived that doesn’t have any children is LESS FIT than someone who is weak/unhealthy/dies young but has 8 kids

Question 25

Group Selection

Answer 25

• when natural selection acts on a group and NOT on an individual
• explains why altruism exists

Question 26

Altruism

Answer 26

• sacrifice the individual to benefit the group

- group should have the traits of the individual so that their traits are not lost

Question 27

Evolutionary Success

Answer 27

• occurs when an allele can increases its frequency in the next generation
• gene has been passed down to next generation
• POPULATION SCALE

Question 28

Biological species must meet the following 3 conditions:

Answer 28

1. must be able to interbreed
2. must be able to produce viable, fertile offspring
3. must do all of the above naturally

Question 29

Does the scenario below result in the creation of a species?

2 different plants interbreed and make fertile offspring, but one plant is pollinated by bees and the other is pollinated by birds

Answer 29

NOT A SPECIES

b/c breeding occurred through an unnatural way

Question 30

Adaptation

Answer 30

genetic change in a population that is due to natural selection

Question 31

Lamarck’s Theory of Adaptation

Answer 31

• Giraffe example – giraffes have a long neck because they had to reach higher for leaves on tall trees so their necks grew
• he only focused on survival, NOT reproduction

Question 32

Specialization

Answer 32

• adaptation of traits to fill different niches
• Ex. trees in one part of the savannah have shorter trees so giraffes here have shorter necks than the giraffes found in a different part of the savannah with taller trees – these giraffes do not harm each other’s fitness because they eat out of different trees

Question 33

Competition between species occurs when ___ overlap

Answer 33

niches

Question 34

How can we avoid competition?

Answer 34

• no common niche between species

- specialization – adapt to environment so don’t need to share resources

Question 35

Inbreeding

Answer 35

• mating between relatives
• increases the frequency of homozygotes and decreases the frequency of heterozygotes
• decreases genetic diversity across a population and increases presence of harmful alleles
• EXCEPTION! naked mole rat can interbreed because harmful alleles have been eliminated from their species

Question 36

Outbreeding

Answer 36

• mating with non-relatives
• increases heterozygotes
• decreases homozygotes
• increases genetic diversity

Question 37

Bottlenecks

Answer 37

• a severe reduction in population size

- usually occurs as the result of a natural disaster (fires, floods, etc)

Question 38

Genetic Drift

Answer 38

• random changes in allele frequencies
• effects of this increase when a population size is small – ex. population of 10 feels the effects of genetic drift more than a population of 10,000

Question 39

Coevolution

Answer 39

• occurs when one species evolves in response to another

- Ex. humans and parasites, parasite has spikes and then human immune system evolves to chop off spikes on the parasite

Question 40

Order of Classification

Largest to Smallest

Answer 40

King Phillip Came Over For Great Soup

Kingdom -> Phylum -> Class -> Order -> Family -> Genus -> Species