Upgrade to remove ads
Only $35.99/year

Test 1 - Biology 152

Terms in this set (70)

What is the theory of Natural Selection?
-'survival of the fittest'

-natural selection, mechanism, in which differential success in the survival and reproduction of different phenotypes (variation, differential reproduction and heredity)
Descent with modification
another term for evolution
Define Genetic Variation:

(3) Sources of Variation? M/R/S
-variations in amongst alleles
-sources of variation:
1) mutations
2) recombination
3) sexual reproduction
Define Mutation:

(3) types: D/N/A
-source of new variation
-3 types:
--deleterious (harmful)
--neutral (most - no effect)
--advantageous (adaptation)
Genotype
-the genes that we have
Phenotype
-allele that is expressed
-variation caused by: genotype + environment
Population
-group of individuals belonging to the same species in the same geographical area
Species
-individuals have the potential to interbreed, and share alleles with one another via reproduction
Gene pool:
-all of the alleles present in the individuals in a species
Define Evolution:
--another term for it is?
-specific theory that explains the origin of the earth's species (biodiversity) by gradual change over time
-principle unifying concept in biology
-descent with modification from common ancestor
Darwin's Beagle Voyage
-he observed what (3) things?
1) taxa showed continental affinities
2) taxa showed similarities b/w extinct and living forms in the same locale
3) unique species groups on Galapagos islands - endemic (only found in a particular location)
When observing the birds... Darwin noticed:
-The birds were similar but their beaks where different
-They ate different things

Overall:
Adaptions and the origin of new species are related processes
(definition of natural selection)
What is Artificial Selection?
-humans selecting desirable traits to propagate the favorable characteristics through the following generations.

(EG: cabbage -> broccoli → kale → cauliflower. )
Summary of natural selection:

4 main points - I/H/E/R
1-individuals do not evolve, populations do.
2-can only act on heritable traits
3-environmental factors vary in space and time
4-natural selection/environment does not create resistant forms, it selects for them.
Define Evolution adaptation: (Natural selection)
-accumulation of inherited characteristics that enhance an organism's ability to survive and reproduction
Define Fitness:
(Natural selection)
-the ability to pass on genes to the next generation
What is the theory of Evolution?
-species are not unchanging
Q:

Populations are currently evolving due to selective pressures acting on them now: T/F
T
-Yes, due to insecticide, pesticide, habitat removal.
-Before these treatments, resistance was not dominant in a population.
-Metamorphosis: changing from one phase of life into another.
(Different that evolution, no mutations etc.)
Allele Frequency vs. Genotype frequency
-allele:
--S-dominant
--s-recessive

-genotype
--ss=50
--Ss=25
--SS=25
How do we measure allele/genotype frequencies?

(3 methods)
1) observable traits
2) gel electrophoresis
3) DNA sequencing
Gel electrophoresis:
-genes ad proteins are separated by size and charge
DNA sequencing
-Get entire sequence for gene of interest
-Single nucleotide differences (G rather than T)
What is 'Modern Synthesis'?
-Darwin's theory of Natural Selection + Mendialian Genetics
-Discrete v. continuous variation
-Several genes are often responsible for a single trait

(continuous expansion of the evolutionary theory)
Natural selection changes the ________________________ _______ ________________
-the frequency of alleles

+ selection: increases frequency of a favorable allele = 'selected for'

- selection: decreases frequency of a harmful allele = 'selected against'

different perspective: trait (phenotype) (ex: height, length, color) (stabilizing, directional and disruptive)
Directional selection selects __________________ one of the two extremes.

-give examples
-shift towards one direction
-ex: light lizard vs dark lizard. the light is more susceptible to die due to their color exposure in their environment. due to this over time, there is a shift towards the dark lizards due to NS.
-ex: antibiotic or pesticide resistance or artificial selection
Stabilizing selection selects _______________________ the extremes.
-ex: the lighter lizard vs the darker: there is a middle ground where the two extremes over time fade out and the middle is the mass of the population due to natural selection

-ex: birth weight for babies - this is stabilizing due to mortality in smaller and larger baby sizes
Disruptive (diversifying) selection is selective against the __________________.

This is the most _________ to occur.
-mean
-rare

-ex: lizards - the lighter lizards vs the darker, the middle ground over time disappears and the two extremes are the only ones that are within the population

-can ultimately lead to two different species
Q: Overtime the amount of water a population of a plant needs to survive gets lower and lower as it adapts to less rainfall. This is an example of:
-directional selection

WHY? the plant is adapting to its condition even with the lack of water
Q: What is the mechanism by which new alleles originate?
-mutations

WHY? its the only way a NEW allele is made
T/F Natural selection and Sexual selection are random processes
FALSE

-Natural + sexual selection are non-random
Sexual Selection is a special case of ___________________ ___________________.

Define and explain. (3)
-special case of natural selection

1) individuals in a population differ in their ability to attract mates (typically males)
2) sexual dimorphism
3) sexual production (inter and intra)
Define Sexual Dimorphism:
-male and female differentiation (look different)

ex: peacocks (males more ornamented), beetles (males with horns, females w/o), lions (male with a 'beard' female w/o)
2 types of Sexual Production:
-intersexual: females choosing males

-intrasexual: males battle it out
ex: seals - the big dominant males take over and get the girls and the young. men hash it out and choose their females.
Another factor on variation is ___________________ ______________ where allele frequencies fluctuate randomly b/w generations.
-genetic drift
Genetic drift leads to: (2)
-reduced variation over time especially in a small population
2 types of Genetic Drift:
-bottleneck effect:
--cheetah original population is not the same as the ones to come with time due to extinction and eliminating of alleles

-founder effect:
--a new population affected by the allele frequencies of its founders
--in time the species is fleeing an area and the population splits from the mainland to the island, the genetic variation is differentiation
(mainland -> islands)
-chance event here is arrival of certain individuals (genotypes on an island)
Sampling error:
-refers to chance events - random departures.

-chance events are more likely in small samples

-in a bigger sample, 50% of two different variables is more likely (heads/tails ex)

-genetic drift = biological form of 'sampling error'
Define Gene flow (migration):
-allele movement b/w populations, over time, reduces differences b/w populations
Why is genetic variation important?
-populations w/ heritable variation

ex: genetic variation has the capacity to adapt to the changing environment
Q: Hunting of American Bison in 1800s decreased the population to 30 individuals and all bison today descended from these.

This is an example of __________.
-genetic drift
What are the five processes that change allele frequencies in a population?
1) mutations (introduces new alleles)
2) genetic drift (frequencies change randomly)
3) gene flow/migration (new gametes or individuals bring new alleles or change frequencies of existing alleles)
4) natural selection (change frequency of certain alleles non-randomly)
5) sexual selection (non-random mating)
Hardy Weinberg Assumptions: (5)
1) no mutation
2) large enough population so that no genetic drift
3) no migration
4) no difference in survival of individuals
5) random mating
If alleles in a population do NOT follow the Hardy Weinberg principle, one of these assumptions must be false.

Therefore __________________ is taking place.
-evolution
Hardy Weinberg Principle:
-frequencies of alleles and genotypes in a population remain constant from generation to generation

-all gametes/alleles are considered one gene pool (two gametes can be chosen at random from the gene pool to represent an individual)
Do natural populations meet the H-W assumptions?
NO - but it provides a good baseline from which to explore the evolutionary processes affecting populations
PP= ________

pp = __________

Pp= ___________

_____ + _____ + ______ = 1

_____ + ______ = 1
-homozygous dominant
-homozygous recessive
-heterozygous

p2 + 2pq + q2 = 1
p + q = 1
What are the (3) factors supporting robustness of HW assumptions?
-1) mutations: weak force and longer time scales (expect for organisms with shorter generation times)

-2) large population sizes are common

-3) selection and/or migration may act to move away from HW equilibrium (random making in most populations leads to HW quickly.
When applying the HW __________________ frequncies with expected under the HW model (null)
-using statistics: Chi-squared test
-identify which genes/alleles are facing selective pressures
Define Taxonomy:
-system of naming and grouping similar organisms
Define Species:
Key evolutionary unit
Biological Species Concept (BSC)
-species are groups of actually/potentially interbreeding populations that are reproductively isolated from other such groups (they can produce viable, fertile offspring)

ex: eastern and western meadowlark
Limitations of the Biological Species Concept: (2)
1 - cannot be applied to all species:
-extinct species (fossils)
-asexual organisms (bacteria)
-difficult to test in most living species

2- complicated by:
-ring species
-hybridization
Define Ring Species:
-complicated

-ex: birds dispersed and mating around a mountain range area

-the red and blue populations of the warbler birds cannot interbreed, but gene flow can still occur b/w these populations through a ring of populations that look south around the himalayas

-both the red and the blue live in regions ajacent to one another, tghe blend of the two occurs in the moutians, where gene flow is displayed leading to hybrization.
Define Hybridization:
-blend of two organisms to form a new one

-ex: red and blue warbler --> blue-winged and gold-winged warbler
Morpho-species concept: (1)
-characterized by body shape, size and structure

---but some species look identical and some look different
Ecological species concept: (3)
-characterized by species' ecological niche
-interactions with living and non-living environment (habitat, diet, etc.)
-complete competitors cannot coexist
Biological Species Concept:
-reproductive isolation
-most useful definition of species, others used to broaden and generalize concept
Define Reproductive isolation:
-biological factors that impede members from two species from producing viable, fertile offspring
----pre-zygotic: prevent mating or fertilization
----post-zygotic: prevent viable, fertile hybrids
Q: A mule (horse-donkey hybrid) is an example of...
-post-zygotic, hybrid infertility
Pre-zygotic barriers: (4)
prevent mating of fertilization

-ecological isolation -- environment
ex: snakes, one lives in the water, other on land.
ex: insects, specialized on different hosts.

-temporal isolation -- time
ex: two different species, one mates during the spring, other during fall.
ex: cicadas, emerge during a certain time of the year and only mate during that time with their own species

-behavioral isolation:
ex: penguins, 'booties.' male rises his leg, women decide on whether to mate or not.

-gamete isolation:
ex: urchin, in the marine environment, women release eggs, men release sperm, and due to the protein coatings surrounding these determine which two will fuse
ex: pollination, the stigma is longer in some plants and due to the length, the pollen can or cannot make it to the eggs
Post-zygotic barriers:
prevent viable, fertile hybrids once the zygote is born

-reduced hybrid viability:
the eggs that are not produced by some hybrids will not hatch

-reduced hybrid fertility:
ex: mule, horse + donkey mating, can survive but cannot reproduce, can also be due to physical attributes that do not make them appealing to others (doesn't have to mean that they are unable to reproduce, just less fertile or less likely to)
Q: Unlike the biological species concept, the morpho-species concept relies primarily on:
-phenotype
How does reproductive isolation arise b/w populations?
- genetic divergence

1) single interbreeding population is split b/w two populations, 2) mutations occur, 3) we take individuals from each population and test them to see if they can interbreed, 4) two diverge genetically b/w mutations occur over time and become fixed in each population over time --> 4) speciation occurs when the two populations are unable to produce viable, fertile, offspring.
Speciation
-occurs when the two populations are unable to produce viable, fertile offspring.
Allopatric Speciation:
-most common

-physical, geographic separation b/w populations
---different for salamander and bird

-gradual change
---subspecies: same species, but do not mate
(ex: snakes that live in different regions and do not mate = the same )

-occurs through:
1-dispersal events: ex: giant storm approaches and blows lizards on a log that makes it to another island, leads to genetic differences over time. (genetic drift-->founder effect)
2-vicariance: an event like a river changing course causes species differentiation. ex: lizards living coherently, then the river comes in b/w and causes two groups to develop and evolve separately.
Peripatric Speciation:
-kind of allopatric speciation

-few 'mainland' individuals disperse to an 'island'
---environment may be different
---small populations leads to pronounced genetic drift

-faster genetic divergence
Result of Speciation is _____________________ ____________________.
-adaptive radiation: effect of rapid evolution diversification, many different species forming, reproductive isolation, peripatric speciation lead to this.
Define Co-speciation:
two closely related associated populations speciate in response to each other and at the same time
-coordinated host-parasite speciation
Sympatric speciation:
-questioned b/c scientist debate whether speciation is relative to geographical differences or not

-natural selection must act strongly to counteract the homogenizing effect of gene flow

-ex: wasps - some favor one apple over the other
_______________ can lead to instantaneous sympatric speciation.
-polyploidy

-hybridization in which offspring are reproductively isolated from parents
-mechanisms = polyploidy: gaining an extra set of chromosomes during a hybrid event
-common in plants but disastrous in animals
Recommended textbook explanations

Biology

2nd EditionJung Choi, Mary Clark, Matthew Douglas
1,296 explanations

Biology

8th EditionCain, Campbell, Minorsky, Reece, Urry, Wasserman
623 explanations

Campbell Biology (AP Edition)

8th EditionCain, Campbell, Minorsky, Reece, Urry, Wasserman
623 explanations

Biology

8th EditionJane B. Reece, Neil A Campbell
623 explanations