Bio 1b 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 that caused a selection of efficient metabolism due to
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