Exam 4 Flashcards
Organismal
studies how an organism’s structure, physiology, and behavior meet environmental challenges (includes physiological ecology & behavioral ecology)
Population ecology
focuses on factors affecting how many individuals of a species live in an area
Community ecology
focuses on interactions among species within the same area
Ecosystem ecology
emphasizes energy flow and chemical cycling among the various biotic and abiotic components
Landscape ecology
how the arrangement of ecosystems in a geographical region affects ecological processes
Global ecology
examines the influence of energy and materials on organisms across the biosphere
Population
a group of individuals of the same species living in an area
Community
a group of populations of different species in an area
Ecosystem
the community of organisms in an area and the physical factors with which they interact
Landscape
a mosaic of connected ecosystems
Biosphere
the global ecosystem, the sum of all the planet’s ecosystems
why are there so many different kinds of organisms?
-many different species
-variation within species and between species
-classification
-mechanisms for creating and maintaining variation
geological evidence:
-fossil record suggests that organisms change
-earth is very old (4.6 billion years), biological life also very old (3.5 billion years)
both Darwin and Wallace notice:
- there are many different species, and also fossils of species that resemble current species
- geographical gradients of change in species
-island species that resemble
mainland counterparts, but are also
different in important ways - organisms seem to have traits that match the conditions of their environment
Adaptations
inherited characteristics of organisms that enhance their survival and reproduction in specific environments
Darwin’s 2 key points
- descent with modification
-species today are descended from
ancestral species that have changed
in time - change of species in time can arise due to natural selection
the process of evolution by natural selection: 4 observations
- individuals in a population vary in their traits
- traits are heritable
- organisms are capable of producing more offspring than the environment can support
- as a result, many offspring do not survive
the process of evolution by natural selection: 2 inferences
- individuals that are well-suited to their environment tend to leave more offspring than other individuals
- over time, favorable traits accumulate in the population
evidence for natural selection and decent with modification
- artificial selection
- direct observations of evolutionary change
- fossil record
- homology
- biogeography
Artificial selection
by controlling survival and reproduction, dramatic change can occur in a short people of time
-wolf ---> dog
Homology
similarity due to common ancestry
Homologous structures
features with similar construction due to common ancestry
-human, cat, whale, and bat all have humerus, phalanges, etc.
Vestigial structures
components that serve no obvious present purpose, but are remnants of the organism’s ancestors
-femur in whales and snakes
Molecular homologues
similar molecular composition of proteins, DNA
Biogeography
the geographic distribution of species
- species on a new island arise from ancestors that arrives from a nearby existing island
Population
a localized group of individuals capable of interbreeding and producing fertile offspring
remember that the process of evolution by natural selection is:
____ + ____ =
variation in heritable traits within a population
+
differential survival and/or reproduction
=
change in traits in a population over time
Heritable traits
traits with a genetic basis
Genotype
genetic composition of an individual
Phenotype
observable characteristics of an individual
Alleles
alternative versions of a gene that produce a different phenotypic effect
variaiton in a genotype …
can give rise to variation in phenotype: selection acts on phenotype
Microevolution
change in allele frequencies in a population from one generation to the next
natural selection acts on __________, but evolutionary change ultimately implies change in ________ in a populaiton
phenotype, genotypes
why is genetic variation important?
-variation is the raw material for evolution
-environment (and thus selection pressure) is unlikely to remain constant
no variation =
no opportunity for adaptive evolution via natural selection
more variation =
less likely that a change in environment will affect all members of population
Gene pool
all of the alleles for all loci in a population
Polymorphism
when there are 2+ versions of a trait within a population
an allele becomes Fixed if
the entire population is homozygous at that locus
Mutation
change in structure of a gene
- only way to generate novel alleles
(new alternatives)
- new alleles mean changes in a
population’s allele frequencies
alternation of gene number or positions
gene duplication, errors in meiosis
Sex reproduction
combining existing alleles in new ways
-meiosis (crossing over and random
segregation of chromosomes)
- fertilization (random union of
gametes
Genetic drift
change in allele frequencies between generations due to random (chance) events
-chance = genetic drift
-tends to reduce genetic variation
through the loss of alleles
- can have positive, negative, or no
effect on level of population adaptation
Genetic drift: Founder effect
-a few individuals separated from source population
-these individuals become “founders” of new population
-allele frequencies in the newly founded population due to random sampling of founders
-often found in island/isolated populations
Genetic drift: Bottleneck effect
-large population suddenly reduces to a small number of individuals due to a random event (ex. environmental catastrophe)
-many individuals and alleles are lost
-even after a population rebounds, the effect of drift is evident in loss of alleles and reduced genetic variation
Gene flow/Migration
change in allele frequencies between generations due to input of individuals or gametes (ex. pollen) from other populations
1.tends to reduce genetic variation
among populations
2. may have positive, negative, or no
effect on the degree of adaption in
the target population
Natural selection (not definition)
is the only one of the four processes of evolution that consistently has positive effects on the degree of adaptation of the target population
Natural selection: Directional selection
favors individuals at one end of phenotypic range
- __/\__
Natural selection: Disruptive/Diversifying selection
favors individuals at opposite end of phenotypic range
-__/~\___ (up, mini dip, up, down)
Natural selection: Stabilizing selection
favors individuals at the middle of the phenotypic range
- /\ (steep)
why are we concerned about small populations?
- population sizes of other organisms may be small
-habitat destruction, modification,
hunting, etc. - small populations experience greater effects of drifts
- bottleneck can introduce drift, even
in “recovered” populations - if populations stay small after
bottleneck, drive continues to
operate
- bottleneck can introduce drift, even
- in small populations, drift can actually become MORE important than selection
- loss of genetic variation, accumulation of deleterious mutations, increasing reduction of population size, and adaptive evolution shuts down
Sexual selection
-natural selection that is related to mating success
-survival isn’t enough- reproduction is important too
Intrasexual selection
acts on traits that affect success in competition with members of your same sex for mates
Intersexual selection
(a.k.a. mate choice) acts on traits that affect success in being chosen for mating by the opposite sex
Sexual dimorphism
differences in size, color, shape, behavvior, etc. between the sexes
