Natural Selection Flashcards
adaptations
inherited characteristics of organisms that enhance their survival and reproduction in specific environments
natural selection
a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals BECAUSE of those traits
artificial selection
humans have modified other species over many generations by selecting and breeding
individuals that possess desired traits
evolution
process of descent with modification
homology
similarity resulting from common ancestry
homologous structures
represent variations on a structural theme that was present in their common ancestor
vestigial structures
remnants of features that served a function in the organism’s ancestors i.e. the skeletons of some snakes retain vestiges of the pelvis and leg bones of walking ancestors
evolutionary tee
a diagram that reflects evolutionary relationships among groups of organisms
biogeography
the scientific study of the geographic distributions of species
genetic variation
differences among individuals in the composition of their genes or other DNA sequences
neutral variation
differences in DNA sequence that do not confer a selective advantage or disadvantage.
mechanisms that contribute to the shuffling of alleles
1) crossing over
2) independent assortment of chromosomes
3) fertilization
population
a group of individuals of the species that live in the same area and interbreed, producing fertile offsprings
gene pool
collection of genes in a population
conditions for hardy weinberg
1) no mutations
2) random mating
3) no natural selection
4) large population size
5) no gene flow
genetic drift
chance events that cause allele frequencies to fluctuate unpredictably
bottleneck effect
a sudden change in the environment, such as fire or a flood, which causes a severe drop in the population
gene flow
the transfer of alleles in or out of a population due to the movement of fertile individuals
directional selection
conditions that favor individuals exhibiting one extreme of a phenotypic range
disruptive selection
conditions that favor individuals at both extremes of the phenotypic range
stabilizing selection
conditions that go against both extreme phenotypes and favor intermediate variants
heterozygous advantage
heterozygous individuals have greater fitness than both homozygous individuals
frequency dependent selection
the fitness of a phenotype depends on how common it is in the population
biological species concept
a species is a group of populations whose members have the potential to interbreed and produce viable fertile offspring but don’t produce offspring with members of different groups.
reproductive isolation
the biological factors that impede members of two species from producing viable, fertile offspring. two types: prezygotic & postzygotic
prezygotic barriers
1) habitat isolation
2) temporal isolation
3) behavioral isolation
4) mechanical isolation
5) gametic isolation
postzygotic barriers
1) reduced hybrid fertility
2) reduced hybrid viability
3) hybrid breakdown
morphological species concept
distinguishes a species by its body shape
ecological species concept
defines a species in terms of its ecological niche- the sum of how members interact with nonliving and living parts of the environment
phylogenetic species concept
defines a species as the smallest group of individuals that share a common ancestor, forming one branch of the tree of life.
speciation
the process of one species splitting into two
allopatric speciation
when gene flow is interrupted when the population is divided into is geographically isolated subpopulations; separate gene pools diverge, mutations occur, and natural selection can alter allele frequencies
sympatric speciation
occurs in populations that live in the same geographical area; can occur if gene flow is reduced by polyploidy, sexual selection, or habitat differentiation
polyploidy
defined as an accident during cell division that results in an extra set of chromosomes
autopolyploid
an individual that has more than two chromosome sets that are all derived from a single species.
allopolyploid
species with multiple sets of chromosomes derived from different species
hybrid zones
where members of different species meet and produce hybrids
punctuated equilibrium
used to describe the periods of apparent stasis punctuated by a sudden change
phylogenetic trees
branching diagrams showing the evolutionary history of a group of organisms; show descent
analogy
similarity between organisms that is due to convergent evolution
monophyletic clade
an ancestral species and all of its descendants
paraphyletic clade
an ancestral species and some of its descendants
polyphyletic clade
distantly related species without their most common ancestor
shared ancestral character
homologous character that is present in a taxon but does not necessarily define the group
shared derived character
a homologous character that is shared between 2 or more species
maximum parsimony
investigate the simplest explanation that is also consistent with the facts
horizontal gene transfer
a process in where genes are transferred though mechanisms such as exchange of transposable elements and plasmids, viral infection and possibly fusions of organisms
endosymbiont theory
posits that mitochondria and plastids were formerly small prokaryotes that began living within larger cells
cambrian explosion
many present day animal phyla appear suddenly in fossils formed 525 to 535 million years ago
paedomorphosis
occurs when reproductive organ development accelerates faster than the other organs, causing sexually mature species to retain juvenile body features
homeotic genes
determine basic features like where legs will develop or the arrangement of petals on a flower
hox genes
provide positional information in an animal embryo, which allows cells to develop into the appropriate structure and location
isomers
compounds that have the same number of atoms of the same elements but different structures and hence different properties
cis trans isomers
carbons have covalent bonds to the same atoms, but these differ in their spatial arrangements due to the inflexibility of double bonds
enantiomers
isomers that are mirror images of each other and that differ in shape due to the presence of asymmetric carbon
function of the endomembrane system
regulates protein traffic and performs metabolic functions in the cell
glycoproteins
secretory proteins made from a carbohydrate group
phagocytosis
smaller organisms of particles are engulfed by the cell
autophagy
lysosomes break down damaged organelles
food vacuole
formed by phagocytosis, surrounds engulfed particles
contractile vacuole
works to pump excess water out of the cell
central vacuole
repository for ions such as potassium and chloride
peroxisomes
specialized metabolic compartments bounded by a single membrane; remove hydrogen atoms and add them to oxygen which forms peroxide
functions of membrane proteins
1) transport
2) enzymatic activity
3) signal transduction
4) cell-cell recognition
5) intercellular joining
6) attachment to cytoskeleton and extracellular matrix
isotonic solution
no net movement of water across a membrane because the concentrations of solution are the same on the inside and outside of the cell membrane; NORMAL FOR ANIMAL CELL, FLACCID FOR PLANT CELL
hypertonic solution
concentration of the solution is lower on the outside of the cell, so water leaves the cell to a lower concentration of water; SHRIVELED FOR BOTH TYPES OF CELLS
hypotonic solution
the concentration of the solute is higher in the cell the water will rush into the cell and cause it to burst. CAUSES ANIMAL CELL TO BURST, NORMAL FOR PLANT CELL
passive transport
form of cellular transport that moves particles from areas of high concentration to areas of low concentrations
facilitated diffusion
passive transportation of solutes across a membrane with the help of protein channels; solutes move from high to low concentrations and this does not require energy
active transport
type of transport that uses energy to move substances in, out, and across the cell
sodium potassium pump
exchanges Na+ for K+ ions across the plasma membrane of animal cells
voltage
electric potential energy
membrane potential
voltage across a membrane
electrogenic pump
transport protein that generates voltage as ions pass across a membrane
exocytosis
the secretion of certain molecules out of the cell.
endocytosis
occurs when the cell takes in large molecules by forming transport vesicles
3 types of endocytosis
1) phagocytosis (cell eating)
2) pinocytosis (cell drinking)
3) receptor mediated endocytosis (a form of pinocytosis)
metabolism
the total of an organism’s chemical reactions
metabolic pathway
begins with a specific molecule and modifies that molecule in order to form a desired product
catabolic pathway
series of reactions that release energy from a given state i.e. cellular respiration
anabolic pathway
series of reactions that store energy or use energy to form desired products i.e. synthesis of an amino acid from simpler molecules
