Chapter 5 Flashcards
What does structure and function reflect?
adaptation of organism to the environment
What is natural selection?
differential success of individuals within the population that results from their interaction with their environment
What are the three rules of natural selection?
1) there is variation
2) it is heritable
3) provides differences in survival and reproduction
What is fitness?
proportionate contribution it makes to future generations
What is evolution?
change over time in a population
What is an adaptation?
heritable trait that evolved over a period of time to increase fitness
What is a gene?
stretch of DNA coding for a functional product (messenger RNA)
What is an allele?
alternate forms of a gene
What is a genome?
collective DNA in a cell
What is a chromosome?
arrangement of genes on a thread
What is a locus?
position of a gene on a chromosome
What makes a diploid?
at any loci, a diploid has two copies of a gene
What are homologous chromosomes?
two copies of a chromosome
What is a genotype?
pair of alleles at a given locus
What is a phenotype?
external, observable expression of the genotype
What is incomplete dominance?
each allele has a specific value that it contributes to the phenotype
What are qualitative traits?
phenotypes that fall into a limited number of discrete categories, like color of hair
What is a quantitative trait?
phenotypic trait has a continuous distribution, like height or weight
What causes quantitative traits?
caused by multiple gene loci or environment
What is phenotypic plasticity?
the ability of a genotype to give rise to different phenotypic expressions under different environmental conditions
What is an example of phenotypic plasticity in plants?
plant size, reproductive to vegetative tissue ratio, and leaf shape is affected by nutrition, light, moisture, and temperature
What is norm of reaction?
set of phenotypes expressed by a single genotype across a range of environmental conditions
What is an example of norm of reaction?
insect bodies changing color in response to temperature during development- development in cold makes a darker color, allowing them to absorb light more
What is developmental palsticity?
different in phenotype due to differing environmental factors; irriversible
What is acclimation?
reversible plasticity, like tolerance to seasonal temperature change
What is genetic differentiation?
genetic variation among subpopulations of the same species
What is a gene pool?
sum of genetic information across all individuals in the population; total genetic variation within a population
How can a gene pool be quantified?
either allele frequency or genotype frequency
What is target of selection?
phenotypic trait that selection acts directly upon
What is a selective agent?
environmental cause of fitness differences among organisms with different phenotypes
What is directional selection?
trait is shifted towards one extreme
What is stabilizing selection?
natural selection favors mean at the expense of the two extremes
What is disruptive selection?
natural selection favoring both extremes
What is the only process leading to adaptation, and why?
natural selection is the only process leading to adaptation because it is the only one that changes allele frequencies
What is a mutation?
heritable changes in a gene or chromosome
What is genetic drift?
change in allele frequency of a population due to random chance
What is an example of genetic drift?
if a parent has few offsprings, not all the genes may be past on and will get lost
What is migration?
movement of individuals between local populations
What is gene flow?
movement of genes between population
What is the Hardy-Weinberg principle?
requency of alleles and genotypes in a population remains constant; no evolutionary change occurs during sexual reproduction itself
What are the 5 rules for the Hardy-Weinberg principle?
1) no natural selection
2) no mutation
3) no genetic drift
4) no migration
5) requires random mating
What is assortative mating?
when individuals choose mating based on some phenotypic trait
What is an example of assortative mating?
female mate choice- when females exhibit a bias toward certain males based on specific phenotypic traits
What is positive assortative mating?
mates are phenotypically more similar to each other than expected by chance
What is an example of positive ossortative mating?
having the same flowering time leads to a higher chance of reproduction
What does positive assortative mating lead to?
increase in homozygotes and a decrease in heterozygotes
What is negative assortative mating?
mating occurs when mates are phenotypically less similar to each other than expected by chance
What does negative assortative mating lead to?
increases heterozygote frequency
What is inbreeding?
mating of individuals more closely related than by random chance
What does inbreeding lead to?
inbreeding depression- increased honozygosity at all loci
What is a cline?
measurable, gradual change over a geographic region in the average of some phenotypic character, like size or color
How can you differentiate plasticity from genotypic variation?
if all individuals in a population share the same phenotype in a controlled environment, it is plasticity; aka a common-garden experiment
What is an ecotype?
population adapted to its unique local environmental conditions
What are zones of hybridizaition?
areas between ecotypes due to gene flow
What is geographic isolate?
extrinsic barrier prevents gene flow among subpopulations
What does geographic isolation lead to?
subspecies with a physical geographic line
What does natural selection favor?
different phenotypes under different environmental conditions
How can fitness act as a trade-off?
maximizing fitness under one set of environmental conditions limits its fitness under different conditions
What is adaptive radiation?
process in which one species gives rise to multiple species that exploit different features of the environment
