BIS2B Midterm 2 Flashcards
Cell Theory (Biologist)
All life is composed of cells
What is life? (Physicist)
Ability to evade the second law of thermodynamics (order to disorder)
What is life? (Evolutionary Biologist)
Ability to evolve- descent with modification
Opairn-Haldane Hypothesis
- Synthesis of complex organic molecules 2. Synthesis of self-replication molecules 3. Packaging of replicating molecules in a membrane- cell
Panspermia Hypothesis
Life originated on another planet and colonized earth
McKay study
meteor from Mars found in Antarctica. contained organic molecules called polycyclic aromatic hydrocarbons and objects that resemble tiny bacteria
Kvenvolden study
metorites that struck Murchison, Australia. found several different amino acids in significant concentrations
Endosymbiotic theory
Chloroplasts and mitochondria may have originally been prokaryotic symbionts living inside primitive eukaryotic organisms. The relationship began when a large eukaryote engulfed a prokaryote but did not digest it.
Cambrian Explosion
In sediments dated from 543-506Myr ago, most of the living animal phyla appeared, including the most diverse groups present today (Arthropoda, Annelida, Mollusca, Chordata)
What caused the Cambrian Explosion?
Increase in oxygen, sexual reproduction, regulatory genes, eyes, and predation
Oxygen’s effect on the Cambrian Explosion
increased atmospheric concentration facilitated the evolution of larger and more active animals
Sexual Reproduction’s effect on the Cambrian Explosion
the advent of recombination and independent assortment of chromosomes during meiosis provided the genetic variation necessary for diversification in body plans
Regulatory genes’s effect on the Cambrian Explosion
evolution of genes that control the transcription of many other genes enabled animals to development diverse and complex body parts
Eyes’s effect on the Cambrian Explosion
the advent of sight enabled animals to forage many different ways leading to different body parts
Predation’s effect on the Cambrian Explosion
evolution of predators selected for adaptations in their prey that enabled them to escape predation (e.g. shells, burrowing)
Ordovician
occurred 450-440 Myr ago, extinction of ~75% of species
Devonian
occurred 364 Myr ago, extinction of ~75% of species
Permian
occurred 251 Myr ago, extinction of ~96% of species
Triassic
occurred 205 Myr ago, extinction of ~65% of species
Cretaceous
occurred 65 Myr ago, extinction of ~76% of species
Point mutation
single base pair substitution in DNA
causes: “Random errors in DNA replication
environmental factors: chemical, radiation
Synonymous
no change in the amino acid during translation
Nonsynonymous
results in amino acid substitution
ex: B-chain hemoglobin gene in humans
Frameshift mutation
caused by insertion or deletion of one or more base sequences which results in a series of amino acid substitutions during translation
pseudogenes
nonfunctional genes
Unequal cross-over
transfer of a segment (gene) from one homologous chromosome to the other
Blended Inheritance
hereditary determinants in the egg and sperm are irreversibly blended
Particulate inheritance
hereditary determinants in the egg and sperm are passed from generation to generation through “discrete particles” (now known as genes). These particles can keep their ability to be expressed while not always appearing in a descending generation. Discovered by Gregor Mendel.
Character
an observable physical feature (e.g. flower color)
Trait
a particular form of a flower (purple)
True-breeding
a particular trait is the only form present when crossed over many generations. Mendel used only such parents
Phenotype
the appearance of an organism
Genotype
genetic constitution of an organism
Homozygous
when an individual has the same copy of an allele (e.g. SS or ss)
Dominant
when an allele is expressed in a heterozygous individual
Recessive
when an allele is not expressed in a heterozygous individual
Law of segregation
when a diploid individual (with 2 copies of each allele) produced gametes, each contains only one copy.
Locus
the site on the chromosome of a gene
Heterozygous
when an individual has different copies of an allele (e.g. Ss)
Law of independent assortment
alleles of different genes assort independently of one another during gamete formation
Linkage
association between genes on the same chromosome such that they do not show independent assortment
Incomplete dominance
when heterozygotes show a phenotype intermediate between those of the two homozygotes
Sex linkage
pattern of inheritance characteristics caused by genes located on the sex chromosomes
Quantitative genetics
the study of continuously measured traits (such as height or weight) and their mechanisms
Quantitative trait
a phenotypic trait that varies continuously (rather than discretely) for different character states
polygenic
they are due to variation at multiple loci (quantitative traits are typically this)
Heritability (h^2)
the proportion of the phenotypic variation that is made up of genetic variance/
a measure of the trait’s ability to respond to selection (h^2)
Selection differential
the difference between the mean of the population and the mean of the selected parents (S)
Genetic variation
variation in alleles within individuals and populations and between populations
Neutral mutation
accumulation of mutations that do not affect fitness
Sexual recombination
crossing over and independent assortment of chromosomes amplifies the number of possible genotypes
Frequency-dependent selection
maintains genetic diversity when the fitness of rare genotypes is higher than common genotypes
Heterosis (hybrid vigor)
when fitness is higher for heterozygotes than for homozygotes
Gene flow
movement of genotypes from one population to another
R
response to selection
Breeder’s equation
h^2=R/S ???
Competition
a process that occurs when individuals share resources that are in short supply
Exploitation
individuals deplete resources by consuming or using them
Interference
aggressive encounters among individuals
Intraspecific competition
among individuals of the same species
Interspecific competition
among individuals of different species
Competitive exclusion principle
two species cannot coexist if they have the same niches (Gause)
Functional Niche
where a species lives and how it obtains resources
Resource partitioning
when species differ in the way they utilize their resources
Limiting similarity
the limit in the degree of overlap that will allow species to coexist
Theoretical studies suggest that it is about 0.6
3 Basic Ways Species May Partition Resources
Diet, Habitat, Time
Character displacement
when species differ more where they are together (sympatric) than where they are alone (allopatric)
Inbreeding
a form of nonrandom mating in which individuals are more likely to mate with relatives than with non relatives
Inbreeding coefficient (F)
probability that a pair of genes are identical by descent
Inbreeding depression
reduction in fitness of inbred organisms caused by increased frequency of deleterious recessive genes
Genetic drift
random change in gene frequencies within populations caused by sampling error
???
the proportion of the population that are heterozygous
Predation
when an animal eats another organism
Typical Predation
when an animal eats another animal
Herbivory
when an animal eats a plant
Parasitism
when an animal eats an organism that it lives on or in
Coevolution
when two or more species affect one another’s evolution
Aposematic
species that are brightly colored to advertise that they are harmful
Mimicry
when two or more species (usually aposematic) resembles one another
Batesian Mimicry
when a non-harmful species resembles a harmful species
Mullerian mimicry
when two or more harmful species resemble one another
Temperature decline
killed species adapted to warm temperatures in low latitude regions and glaciation killed all species in high latitude regions
Sea level decline
occurred during all 5 mass extinctions. Marine species became extinct on exposed continental shelves
Volcanic eruptions
bury organisms, reduce sunlight (photosynthesis), emit sulfur oxides (acid rain dissolves calcium carbonate)
Plate tectonics
formation of supercontinents (Pangaea) reduced sea levels and caused volcanic eruptions. Probably largely responsible for Permian mass extinction
Asteroids
cause massive dust clouds that reduce sunlight. Probably largely responsible for Cretaceous mass extinction
Gamma-ray bursts
from far away supernovae destroy the ozone layer which protects organisms from too much UV light
Community
a set of species living in a particular place
Community Ecology
the study of multiple species interactions and abiotic factors on the structure and dynamics of communities
Predator-mediated coexistence
when predators reduce prey populations and thereby prevent competitive exclusion of prey species, increasing species diversity
Disturbance-mediated coexistence
when abiotic disturbances reduce prey populations and thereby prevent competitive exclusion of prey species, increasing species diversity
Competition Hypothesis
species are more specialized in the tropics, allowing more species to coexist
Predation-Distubance Hypothesis
Predation and abiotic disturbances are at an intermediate level in the tropics allowing more species to coexist
Succession
temporal change in community composition
Primary Succession
begin on bare rock or sand (no soil)
Secondary Succession
begins on soil
Climax
final stage
Supports the Facilitation Model
early species modify the environment in a way that allows later species to colonize
Allele
different forms of a gene (e.g. S, s)
