what is a species
- a group of individuals that interbreeed and produce fertile, viable offspring. One species is distinguished from another when, in nature, it is NOT possible for matings between individuals from each species to produce fertile offspring
what is biological species concept
states that a species is a group of naturally interbreeding individuals that produce fertile offspring and are reproductivly isolated from other such groups
Identify and explain the four main mechanisms leading to evolution?
- natural selection
- genetic drift
- gene flow
- mutations
natural selection
- increase in allele frequence produces adaptations. it is not progressive, it is reactive, meaning it reacts to environment.
-equalizes allele frequency; genetic sharing
-thory by which evolution occurs - 4 patterns: directional, divergent, sexual, artifical
genetic drift
- a random event that changes allele frequency in population due to chance
- fluctuations in allele frequency
- usually decreases genetic diversity and decreases allele frequency
- random with respect to fitness
- creates a seperate population
- more noticable in smaller populations
- not adaptive
- bottle neck effect
- ex cheetahs in zoo
-narrowing
gene flow
- movement of alleles from one population to another
- immigartion and emmigration
- equalizes gene frequency between source and recipient pop
- random wrt fitness, but tends to decrease genetic diversity between populations
- opposit to genetic drift
- soy bean aphids- blew to n america from other continnts
- ex. caribou of 2 different sides of oil pip. 2 different caribu populations. oil pipline is removed after 50 years and the caribous combine
mutations
- restores geneti diversity by creating new alleles
- causes random changes in genes, mst often leads to deleterious alleles (alleles that decreases fitness)
- rarely lead to benefical allels (alleles that increase fitness)
- relatively slow acting
- 1 individual and then spreads to others in population over generations
- more significant in organisms with short generation times because they eveolve faster
- introduces new alleles
-ex.
Why is artificial selection natural selection? Why might we consider it different?
- yes because it is still a change in allele frequency
- an adaptation to a pressure
- different because humans are the selective pressure compared to a natural pressure suh as flooding, poor nutients, weather
divergent selection
-selects against intermediate phenotype
-decreases gentics diversity in 2 or more directions
- can lead to specisiation through adaptive radiation
- ex. galapgoes finches- beak size varoed based on seed type avalible
directional selection
- increase frequency of one allele
-more noticable in a smaller population - decreases genetic diversity in one diection
- ex. cliff swallows (increased body size could surive harsh winter compared to smalled body size. increased body size allele frequency increased in population
sexual selection
- selective pressure is mate choice
-specific traits that increase individual fitness - usually decreases genetic diversity in one direction per sex (can increase)
- 2 mechanisms: mate choice and functional ecology
- Mate choice: females pick mates based on specifc features, ex peacocks
- Funxtional ecology- environment influences sexual selection, ex. sunfish, ex. anglerfish (male much smaller than female)
artifical selection
- selects for specifi traits that are desired for human selection
- usually decreases genetic diversity (ex. chicken breasts)
- can increase genetic diversity (tulips, roses)
- human choice is selective pressure
- ex. pigeons. darwin published variation of plants and animals under domestiction
what are the mechanisms of speciation
allopatry, parapatry, sympatry
Why is genetic drift an important issue concerning the conservation of species?
- alleles can be lost due to genetic drift. it is random so there is no control
- drift can cause even harmful alleles to increase in frequency by chance alone
- drift decreases genetic variation in populations, potentially decreaseing population’s ability to evolve in response to new selective pressure
- bigger impact in smaller populations
what is a genotype
underlying genetic makeup, consisting of both physically visible and non-expressed alleles of an organism
what is a phenotype
observable traits expressed by an organism
Why is the Hardy-Weinberg principle considered a null hypothesis?
mathematical model to analyze the consquence sof mating amoung all indivudals in a population. randomly combines all gametes produced in each generation into a single pool called the gene pool
- redicts the genotypes of the offspring that the population would produce, as well as the frequency of each genotype
- is a null hypothesis because it only stands under these conditions:
- no natural selection
- no genetic drift
- no gene flow
- no mutations
- no random mating
does not account for evolution therefor is null
- two fundamental claims : 1) if the frequencies of ‘A’ and ‘a’ equal p and q, then the frequencies of genotypes AA, Aa, and aa will equal p^2, 2pq and q^2, respectivley for every generation 2) when alleles are transmitted according to the theory of inheritance, these frequencies DO NOT change over time
what is a null hypothesis
- the hypothesis that there is no significant difference between specified populations, any observed difference being due to sampling or experimental error.
Using the terms ‘allele’, ‘dominant’ and ‘recessive’, differentiate homozygous and heterozygous geneotypes
in a homygous genotype, two identical alleles are inheritible and therefore that allele is expressed becasue it is the only one present. In heterozygous genotype, two different alleles are inheritited. there is a dominant (A) and an recessive (a). in heterozygous, (Aa) the dominant is expressed. in homozygous, there is either AA or aa.
specization
- the generation of novel, reproductivley isolated population
- one might say that the ultimate result of evolution is speciation
- begins when gene flow between populations is decresed
adaptive radiation
a population of one species disperses throughout an area, and each finds a distinct niche or isolated habitat
sympatry
- most complex
ex. fruitflies - speciation that occurs in the same
geographic space - One form of sympatric speciation can begin with a serious chromosomal error during cell division. In a normal cell division
event chromosomes replicate, pair up, and then separate so that each new cell has the same number of chromosomes. However,
sometimes the pairs separate and the end cell product has too many or too few individual chromosomes in a condition that we
call aneuploidy
parapatry
- involves hybrid depression
- hybrid occurs and has increased fitness in that region
- foundation for speciation
- over time, the new species can be formed through hybrid and hybrid mating
- becoems new speices when hybrid can no longer mate with origional species/ cannot create fertile offspring
- ex. orioles. two populations. they mated an created a hybrid. The hybrid had increased fitness. As more hybrids were created, they eventually mated and continued to produce offspring because they had increased fitness. became seperate species
allopatry
- simplest
- spacial
- ivolves geographic seperation of populations from a parent specie and subsequent evolution
-ex. owls can no longer mate because a mountain seperated them
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what is life9
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biological organization6
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what is biodiversity9
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what is evolution21
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evolutionary processes28
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cell theory, structure and function22
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Cell evolution14
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characteristics of life4
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introduction to metabolism: extremophilie21
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biochemical cycles16
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social psychology15
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Intro to Physiology19
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Intro to Intra- and Inter-Cell Communication21
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Introduction to food web and ecosystem ecology11
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diffusion and exotoxicology5
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psychology of addiction8
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psycho-physiology of technology5
