Bio 1b_8 Flashcards

Terms Definitions
4 ideas that are the basis of natural selection
Variability, heritability, variation in survival and reproduction, selection
3 components of a successful theory of evolution
(1) The fact of evolution. We can observe that organisms change over time. (2) The pattern of evolution. How exactly do species change over time? Is the change abrupt, or do species change gradually? (3) The mechanism (process) of evolution. What causes species to change over time?
Problem with finding a mechanism
To find a possible mechanism, we must make an assumption: Uniformatism
: Proccesses that occur today, must have occurred in the past
Uniformitarianism cont.
1. alternative is that processes were different than they are today: supernaturalism or magic 2. It does not mean that all processes are slow ad gradual--> abrupt processes: volcanos, earthquakes, floods. 3. Uniformitarianism does not imply that rules governing change in the past (and present) are perfectly understood or predictable
Theory that Darwin and Wallace comprised
Descent with modification
Darwin's significant contribution
Darwin also had something to say about the pattern of evolution. He argued (strongly) that species change gradually over time. Most importantly, Darwin was the first to propose a mechanism of evolution, called natural selection.
Darwin's observation of domestic animals
1. Individuals vary 2. Heritable: offspring resemble their parents 3. Selective breeding: breed selectively for certain traits
Variation in the Wild:
degree of variation in the wild seems to be the same as domesticated animals
Darwin and Natural Theology
He debunked the belief that all organisms lives harmoniously in the wild--> struggle for existence is the infinite growth of individuals
Natural selection
Individuals with an advantageous trait for survival and reproduction will reproduce more offspring--> next generation will produce more offspring--> their population is favored
Evolution species vs: individual
An individual does not evolve, the composition of the traits of the individual change which causes the evolution of the species.
Transitional forms
gradation between species: 1) rocks have transitional forms--> however the fossil record is missing such that there is a rarity of fossilization 2) transitional forms are not present among individuals: constantly evolving, therefore the intermediate species are not seen.
Why don't we see transitional forms?
imperfections in the rock forum
Comparison to special creation
1. Imperfection of adaptation: although species strive to be more perfect than the predessesor, yet common ancestry inhibit this perfection--> i don't want to be different: example= webbed feet of geese 2. homology: similarity of structures in different species used for different purposes (descent with modification) 3. Similarities during development but change--> common ancestry. 4. Rudimentary organs:
Proof of common ancestry
bone structure in humans, horse, bats, etc...
3 processes that affect genetic make up
gene flow, genetic drift, nonrandom mating
NeoDarwinism theory of evolution
Species evolve because of the evolution of allele frequencies due to natural selection and other factors
any change in the nucleotide sequence of an organism's DNA
2 types of mutations
deleterious and neutral
Is there another type of mutation??
Beneficial: mutation can restore genetic variation that other evolutionary processes removed:
Gene Pool
Sum of all copies of all alleles at all loci found in a population
favored trait that evolves through natural selection
gene flow
Migration of individuals and movement of gametes between populations--> if gene flow is disturbed--> possible speciation
genetic drift
random exchange in allele frequencies from one generation to the next
(variant of DNA sequence) different forms of a gene A, B, a, b, etc
allele frequencies
proportion of each allele in the gene pool
genotype frequency
: proportion of each genotype among individuals
translation process for genes
homology in the genome
genes being similar but varied amongst a wide range of species
Genetic code
(with minor alterations) it is shared amongst all of life
location of a gene smallest possible is a single nucleotide
combination of alleles that a species has at a locus
a cell that fuses with another cell during fertilization (forms a zygote)
the trait of physical characteristic that is seen --> caused by the genotype (phenotype frequencies are caused by genotype frequencies
H-W frequencies
They do not depend on the genetype frequencies of the parent--> only on the allele frequencies
Hardy Weinberg conclusins
Allele frequencies do not change due to random mating--> will stay the same: if not it is due to outside forces
frequency and recessive gene
Alleles that cause recessive genetic diseases are in low frequency.
Deviation between observed and H-W allele frequencies in Sickle Cell anemia
There are fewer SS genotypes, and an increased AS frequency because there is a greater chance of survival for the heterozygous AS genotype: example of balancing selection
What causes allele frequencies to change in a population?
mutation, natural selection, genetic drift, and gene flow (migration)
point mutation
change in a single nucleotide (very low probability in plants and animals--> high in bacteria and viruses)
3 types of mutations
deletion, insertion, and duplication
small or large pieces of a chromosome--> second copy of the gene or whole chromosome: In humans, individuals born with 3 copies of chromosome 21 (trisomy 21) have Down’s syndrome
Importance of fitness in mutations
If individuals with different genotypes differ in their chances of survival and reproduction, then there are differences in fitness that cause allele frequencies to change. Average fitnesses of different genotypes may depend on the environment.
Types of selection
directional, balancing, purifying,
Directional selection occurs when one allele results in higher rates of survival and reproduction.If a population initially contains only aa individuals and an advantageous allele A is created by mutation, then the frequency of A will increase every generation because of natural selection.
Example of Directional selecion
Native Americans and some other groups are at a relatively high risk for type II diabetes (non-insulin-dependent diabetes) as adults. This is due to the frequent famines selecting of efficient metabolism that causes type II in the modern diet.
Removal of a deleterioud mutation, especially common when the population had initially only been 1 genotype
If a heterozygous gene has a higher chance of fitness than the homozygous--selection will increase the frequency of both alleles
example of balancing
Malaria and sickle cells: AA are more likely to die that AS--> produce more AS
Genetic Drift: specifics
it's more powerful in small populations; probability of an allele being fixes = 1/2N--> The rate of change in allele frequency because of genetic drift is small in large populations and larger in small populations.
founder effect vs bottleneck
A bottleneck is a reduction in size of an existing population while a founder event is the establishment of a new population of smaller size.
example of bottlenecks
Cheetahs probably experienced an extreme bottleneck in size. There are so ew genetic differences between individuals that skin can be successfully grafted between unrelated individuals, something that is impossible in other mammals.
founder effect
Isolated populations founded by a few individuals may have some genetic diseases in high frequency that are rare elsewhere.
example of founder effect
Huntington’s disease (HD) is a late-onset dominant lethal condition. In the US population, the frequency of HD is about 1/10,000. The gene causing HD was identified by studying an extended family in San Luis, Venezuela, where almost 25% of the residents develop HD. One of the individuals who founded San Luis carried an HD allele.
neutral alleles
they have no effect on fitness-->example, mutation that changes the DNA sequence, but has no effect on amino acids ... also, all neutral alleles will be lost in a population, yet the rate at which it is lost is determined by population size
Gene Flow: specific functions
Reduces differences among populations
Gene Flow and gmos
Libery rice was resistant to Libery herbicide-->1998-2001 it was used in a few states in the United States but it spread to other states, and through trade, this strain of rice, LL601, was found in Europe. This caused japan to ban the import of American rice to prevent the contamination of their prouduct
Gene flow and animals:
Interbreeding between wild salmon and fish raised in hatcheries--> domesticated grow faster but have higher death rates. Interference
What is the approximate rate of substitution of neutral mutations in animals?
2*10^-9 per nucleotide per year
Natural selection favors which mutation?
Natural selection, in this instance, will favor mutations that have a beneficial effect early in life, even if the same mutation has a deleterious effect late in life. --> 50-60 years, even when kept in benign environments. Why do he evolutionary explanation for aging is straight-forward: Organisms deteriorate because natural selection acts more effectively in young than in the old.
Fruit fly experiment
Mutations that lead to an extended life span--> put a stress on late acting mutations
Ecoli experiement
Example of beneficial mutation: Normally, the cultures are grown at body temperature (37°C). Wichman and Bull evolved the viruses to grow well at high temperature (43°C). They were able to completely sequence a sample of the evolved φX174 to see which mutations were responsible for the adaptation to high temperature.
Example of Natural Selection in the wild
Peter and Rosemary grant: bird on an island's beak size correlates with seed availability
Example of Natural Selection in the Wild, pt 2
Hopi Hoekstra and Michael Nachman studied the coats of pocket mice in the Pincates Lava Flow. Pocket mice have coat color that matches the substrate to which they live on. Is it adaptative? What is the genetic cause? Hoekstra noticed a similar coat color mutation among house mice, which helped her realize Hence, she was able to use a candidate gene approach. She found an association between dark hair color and four mutations in Mc1r. Because coat color affected predation: owls could see the mismatched ones better--> example of adaptation and natural selection--> survival.
2 chromosomes
cell division necessary for reproduction: gametes are formed
If you have 4 chromosomes in a loci
each chromosome has a 50/50 chance of becoming a gamete. Example: A, a, B, b, you'll have 4 gametes--> chross over
creates individuals that are different from either of their parents--> siblings differ from each other
Isogamy vs. ansogamy
Isogamy: gametes of the same size. (funghi or algae) Ansogamy: different size gametes
Hermaphrodite vs. separate sexes
most plants are maphrodites, for example peas, can self-fertilize; some, for example slugs, cannot. --> example of sequntial hermaphrodite: at one point they are both--> sex evolves (male-->female {clams} or vice versa)
Genetic vs. Environmental Sex determination
Humans: genetic (XX or XY) Bees: (ZW female, ZZ male) Environmental: Temperature dependent sex determination (turtles and crocodiles: egg at low temp=male, high=female) females are hotterrrrrr
Asexual Reproduction
forms offspring identical to the mother
Classes of asexual reproduction
Aproximus: plants Parthogenic: animals both sexual and asexual: aphids
Different from asexual reproduction--> Siblings produced by self-fertilization have genotypes that differ and from their parent.
Sexual Reproduction
Costs: energy (finding a mate); parasites (animal stds) two-fold cost of sexual reproduction
Two-fold cost of reproduction
Asexual reproduction: 2x as many daughters as sexual
Why hasn't natural selection removed sexual reproduction?
genetically diverse offspring are better able to survive in different conditions. And the elimination of deleterious mutations--> recombination --> less likely for the mutation to be on the same chromosome--> more rapid evolution--> you can break up a mutation (good or bad) on a specific chromosome--> produce two gametes
Sexual Selection
explains sexual dimorphism: different sexes look different. ex of a peacock feather and the birds of paradise: their long tails are not beneficial but they still have them
Darwin's struggle for existence
Both a struggle to survive and a struggle to reproduce
Female Choice
Female preference effects the adaptations of the male (birds of paradise) --> causes males to have highly elaborate traits that seem maladaptive (secondary sexual traits)
Male-Male competition
it is an intrasexual example of selection. include within group dominance, female- defense polygyny, territorial polygyny, and lekking (where the males compete for a position in the lek). Sheep and antlers: large antlers--> better at fighting--> females mate with them
Two types of female choice
resource-based (good genes= ultimate or indirect benefits--> example: female chooses a male based on his coat color: red is appealing to her, birds of paradise--> also refers to survival, long tail= strong) ) or ) (direct or proximate benefits such as egg size) ex: bush crickets providing spermetaphors which increase egg production; nonresource based or choosiness
Types of male-male competition
1. within group dominance (hierarchy) 2. female defense polygyny (male elephant seals protect female elephant seals) 3. territorial defense polygyny (waterbucks headbutting) lekking
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