Midterm 2 Flashcards
(88 cards)
1
Q
Define character
A
An observable, physical, heritable factor that varies among individuals (hair color, height)
2
Q
Define trait
A
The alternative forms of a character (brown/black hair)
3
Q
Define true-breeding
A
Organisms that “breed true” with respect to a particular trait - breeding within only gives rise to offspring with that trait.
*Self-pollination would produce progeny that all have the same phenotype as the parent. e.g. If a plant variety was true breeding for a dominant train, all progengy would have dominant trait
4
Q
What is the law of segregation?
A
Two alleles for a heritable character separate from each other during meiosis and end up in different gametes.
5
Q
What is a test-cross?
A
A cross between a dominant phenotype (S?) and a homozygous recessive (ss).
6
Q
What is the law of independent assortment?
A
Alleles for different traits assort independently of each other during Meiosis
7
Q
Why did Mendel use pea plants?
A
- It’s easy to control mating in peas
- Peas have many easily-scored,
true-breeding, heritable traits
- Relatively short
generation times (one year), so
many experiments could be performed
- Peas make lots of offspring
8
Q
Define qualitative variation
A
Either-or of alternative traits (red or pink)
9
Q
Define quantitative variation
A
Many genes affect a trait and there are alleles at different loci.
Ex. Human height affect by alleles at 180 loci
10
Q
Define evolution
A
Changes in allele frequencies in populations over time
11
Q
Define population
A
A group of same species organism living in the same area at the same time. Interbreeding occurring
12
Q
What process forms new alleles?
A
Mutation
13
Q
What is a point mutation?
A
Substitutions of a single base in a gene. There can either be a protein change at higher levels or no protein change (silent point mutation).
14
Q
What is an insertion/deletion mutation?
A
Addition/loss of one or more bases.
- Multiple of 3 bases results in loss of amino acid
- Non-multiple of 3 results in ALL amino acids changing (frame-shift)
15
Q
What is a frame-shift mutation?
A
When a non-multiple of 3 amount of bases are inserted/deleted resulting in a change of ALL amino acids in that gene.
16
Q
What is gene duplication?
A
17
Q
What organisms are more susceptible to mutations?
A
Organisms with rapid generations times (divide frequently)
18
Q
How does a mutation affect the phenotype of an organism?
A
Mostly negative
Sometimes neutral but RARELY positive
19
Q
Are mutations goal directed?
A
No they arise randomly
20
Q
How do mutation and sexual reproduction generate variation?
A
Mutation makes new alleles
Sexual reproduction shuffles alleles
21
Q
A diploid organism can have at most how many different alleles at a particular locus?
A
2
22
Q
Define gene pool
A
The sum of all copies of all alleles at all loci in a population.
23
Q
What does it mean if a population is monomorphic or fixed at a particular loci?
A
There is only one allele at this locus
24
Q
What are the 5 conditions for the Hardy-Weinberg Equilibrium?
A
- No mutation
- No gene flow
- Large population size
- No natural selection
- Mating is random
25
What are the 5 mechanisms of evolution?
1. Mutation
2. Gene flow
3. Genetic drift
4. Natural selection
5. Nonrandom mating
26
Define gene flow
The movement of genes among populations which introduces new alleles. Tends to make populations more similar to one another
27
Define genetic drift
Random changes in allele frequencies due to random **sampling errors**. Small subset of population that do not reflect true allele frequencies reproduces.
\*Strongest effect on **small populations**
28
What are the two special cases of genetic drift?
1. **Bottleneck** - Population reduced dramatically (killed) resulting in reduced genetic variation
2. **Founder Effect** - Immigrants break off and start new population
29
Define natural selection
Differential **survival/reproduction** of individuals in a population based on **heritable** variation in their **phenotypes**
30
What are two requirements of natural selection?
**Heritable variation** in **phenotype** and that variation affects **survival/****reproduction** of individuals
31
Define relative fitness
The **contribution** an individual organism makes to the **gene pool** of the **next generation** **relative** to the **contribution** of others in that population
32
What are adaptations?
**Heritable traits** that **increase** survival/reproduction rates
33
What is Stabilizing Selection?
When the "**Average**" phenotype is most likely to survive
34
What is Directional Selection?
**Phenotypes** at **one end** of the distribution are most likely to survive (higher relative fitness)
35
What is Disruptive Selection?
**Phenotypes** at **both ends** of the distribution are most likely to survive (highest relative fitness).
\*Mean phenotype has lowest relative fitness
36
Why doesn't natural selection edit out alleles with least relative fitness?
1. Hard to delete out recessive alleles
2. **Heterozygote advantage** - Heterozygote RBC are better when malaria is present
3. **Frequency-dependent selection** - allele frequency fluctuates back and forth. Ex: "left-mouthed" "right-mouthed" fishes
37
Why doesn't natural selection create "perfect" organisms?
1. It can only act on **existing variation** in a population
2. Has to operate within **universal physical/chemical properties**
3. Limited by **historical constraints**
4. Adaptations usually require **trade-offs** among different traits
38
What is non-random mating?
When individuals choose mates with a particular genotype
1. Prefferential mating with individuals of a different genotype - **heterozygote** frequency increase
2. Prefferential mating with individuals of the same genotype - **homozygote** frequency increase
\*DOES NOT affect allele frequencies\*
39
What is sexual dimorphism?
Differences in appearance between male and females of the same species
40
What is sexual selection?
Reproductive success resulting from competition for fertilization
\*DOES affect allele frequencies\*
41
Compare intrasexual and intersexual selection
Intrasexual - **competition between 2 males** for the female (No female interaction)
Intersexual - Where **female chooses** the male based on a physical trait
42
What is the good genes hypothesis?
Females choose males since phenotype may be a reliable indicator of good traits so her offspring will be high quality
43
What is the sexy son hypothesis?
Female selects best phenotype becuase her offspring will be more likely to get a mate
44
What are the only evolutionary mechanisms that produce adaptation?
Selection (natural and sexual)
45
Does selection (natural and sexual) favor traits that are good for the population or the individual?
Individual
46
Define immutable
Not changing over time.
e.g. Early in science, biologists thought species were immutable
47
What is the morphological species concept and why do most biologists not use it?
States that organisms that **look alike** are of the same species.
This is problematic because some different species look very similar (**cryptic species**)
or
Some times males/females/juveniles of the same species look different
48
What is the biological species concept (BSC)?
Species are groups of actually/potentially **interbreeding** populations that are **reproductively isolated** from other such groups
49
Compare prezygotic and postzygotic reproductive barriers
Prezygotic - **Before** fertilization
Postzygotic - **After** fertilization
50
What are the 5 prezygotic reporductive barriers? Explain them.
1. **Habitat** isolation - different habitat (land and water)
2. **Temporal** isolation - different mating times during the year
3. **Behavioral** isolation - individuals reject potential mates because of their behavior (breeding calls of frogs)
4. **Mechanical** isolation - Genitalias don't work together (shape, size, position)
5. **Gametic** isolation - sperm and eggs don't bind successfully
51
What are the 3 postzygotic reproductive barriers? Explain them.
1. **Reduced hybrid viability** - hybrid offspring have developmental problems
2. **Reduced hybrid fertility** - hybrid offspring have low fertility or are completely sterile
3. **Hybrid breakdown** - F1 generation is fine but F2 generation has survival/reproducing problems
52
What was Lamarck's hypothesis? Who disproved it?
Traits change by **use or disuse** and these changed traits are **heritable (inheritance of aquired traits).**
August Weisman disproved by cutting off the tails of mice and breeding them with one another and DISPROVED the inheritance of aquired traits hypothesis.
53
What 4 factors did Darwin base his hypothesis on?
1. Voyage of **The Beagle**
2. Knowlegde of "**artificial selection**"
3. Knowledge of **variation** in nature
4. Knowlege that all species have **potential** for rapid growth but **rapid grown is rarely seen in nature** - so some individuals die off
54
What is the Dobzhansky-Muller model?
When a **single** ancestral population dets divided into **two separte populations** and they **evolve independetly**
55
What is allopatric speciation?
"allo" = different; "patric" = fatherland
Population are initially separated geographically
56
What is a founder event?
When a group of individuals from a population cross a barrier to form a new isolated population.
Will probably lead to a founder effect - reduced genetic variablitly
57
What is sympatric speciation?
"sym" = together with; "patric" = fatherland
Reproductive isolation WITHOUT physical barrier
58
What are the 3 types of sympatric speciation? Explain them
1. **Disruptive selection on habitat preferenced -** mating happens on preferred habitat only and speciation occurs over time ( flies on hawthorn fruit and flies on apples)
2. **Sexual selection** - Females choice of males to mate with based on male triats like coloration
3. **Polyploidy** - whole sets of chromosomes are duplicated
59
Compare autopolyploidy and allopolyploidy
**Autopolyploidy** - duplication within species
**Allopolyploidy** - combining chromosomes of two different species
\*Happens via errors in mitosis or meiosis
60
What is autopolyploidy and in what organisms does it often happen?
**Mitotic error** leading to **tetraploid cell** which undergoes meiosis producing **diploid gametes**. If diploid sperm fertilized diploid egg - offspring is **tetraploid**
Often happens in organisms that can **self-fertilize** (plants)
61
Why does polyploidy lead to speciation?
When a tetraploid mates with a normal diploid, **BAD** things happen. Tetraploids become isolated from diploids
62
What is allopolyploidy?
Two **different species** mate forming a hybrid. (mule)
63
What is hybridization? Does hybridizaion occur in allopatric or sympatric speciation?
When populations that are becoming reproductively isolated begin to interbreed
Sympatric ONLY
64
What are the 3 outcomes for hybridization?
1. **Fusion** - if substantial gene flow occurs, they fuse back into one
2. **Stability** - Hybrid zone remains constant but hybrids are **less-fit** than pure-breds
3. **Reinforcement** - natural selection strengthens prezygotic barriers. Mating is favored within species and hybridization is avoided
65
Reinforcement only occurs in \_\_\_\_\_\_\_\_
Zones of **sympatry** (where two species overlap)
66
Define evolutionary radiation
Rapid diversification of many species from a single ancestral species
67
What 4 factors determine the rate of speciation?
1. Limited movement/dispersal
2. Specialized diets; speciation in herbivore bugs higher than predatory bugs
3. Speciation rate higher in animal-pollinated plants vs. wind pollinated
4. Strong sexual selection
68
What are different alleles?
Different DNA sequences (version of the same gene) found at the **same locus** on **homologous chromosomes**
69
If each parent can produce 100 genetically distinct gametes, how many genetically distinct offspring can two parents produce?
100 X 100 = 10,000
70
What are two important observations Darwin made that helped shape his theory?
1. Organisms within a populaiton vary
2. Organisms produce more offspring that can be supported by the environment
71
What is artificial selection?
The breeding of plants and animals for particular traits by humans.
e.g. One example is the breeding of cows to produce offspring with higher milk yields
72
The smallest unit that can evolve is a \_\_\_\_\_\_\_\_\_\_
population
73
What is convergent evolution?
The independent evolution of **similar traits** in **different lineages**
74
If a new species of plant is to be produced by means of allopolyploidy from two parental species that are 2n = 4 and 2n = 8, how many chromosomes would you expect in the somatic cells of the new species?
12
The two gametes would be n = 2 and n = 4. They would combine for a total of 6, which after doubling would be 12.
75
A new species can arise in a single generation by \_\_\_\_\_\_\_\_\_\_.
**Polyploidy** - The diploid chromosome number changes
76
In a hybrid zone, what could lead to reinforcement?
1. Reduced hybrid fertility/viability
2. Sexual selection
3. Hybrid breakdown
77
According to the punctuated equilibrium model of evolution, \_\_\_\_\_\_\_\_\_\_.
The tempo of evolution consists of **abrupt episodes of speciation** followed by **long periods of equilibrium**.
78
What is a polytomy?
Where a common ancestor has more than 2 sister taxa
\*Node 5 below\*
79
What is a clade?
A taxon that includes a common ancestor and ALL of its descendants
80
What is an ancestral trait?
A trait present in a common ancestor
81
What is a derived trait?
A trait that has changed from the ancestral version to something new
82
Define homologous trait
Similar traits shared between 2 or more taxa inherited from **common ancestor**
83
Define analogous trait
Similar traits shared by two or more taxa for reasons **other than ancestry**. Evolved via **convergent evolution**
84
Why are shared derived traits more useful than shared ancestral traits?
Because they are homologous traits that are found in two or more members of the ingroup, but not in the outgroup. These help us **identify subgroups** within the ingroup.
85
What are monophyletic groups?
Groups that consist of a common ancestor and all of its descendants – aka, a **clade**. This is good!
86
What are paraphyletic groups?
Groups that consist of a common ancestor and some (but not all) of its descendants. Bad!
\*Group in Pink\*
87
What are polyphyletic groups?
Groups that don't include the most recent common ancestor of the group. Bad!
\*Group in yellow\*
88
