Download Chapter 5 Outline

Chapter 5 Outline
-biological evolution: genetic change in the populations of organisms
across generations
+changes: appearance, functioning, behavior
+results from random genetic changes, either by natural selection or
randomly
Natural Selection
-natural selection: process by which traits that enhance survival and
reproduction are passed on more frequently to future generations that
those that do not, thus altering the genetic makeup of populations
through time
-Charles Darwin and Alfred Russell Wallace both proposed that natural
selection was the cause of evolution
-reasons for natural selection:
+organisms face a constant struggle to reproduce and stay alive
+organisms strive to reproduce only offspring that can survive
-adaptation: trait that promotes success in a given environment
-evidence of natural selection:
+selective breeding of domesticated animals
+artificial selection by only allowing like to breed with like
*crops, dogs, etc.
Genetic Variation
-mutations: accidental changes in DNA; provide genetic variation,
whether good or bad
-sexual reproduction varies genetics through the mixing of genomes
(recombination)
-ways natural selection affects genetic variation:
+directional selection: selection that drives a feature in one
direction rather than another (ex: faster to slower)
+stabilizing selection: produces intermediate traits to preserve the
status quo
+disruptive selection: traits that diverge from the starting condition
in two or more directions
-environment affects how natural selection will act
-natural selection not only weeds out unfit individuals, but it also helps
to diversify and expand traits that may lead to new species
Biological Diversity (Biodiversity)
-biodiversity: the sum total of all organisms in an area, taking into
account the diversity of species, their genes, their populations, and their
communities
-species: particular type of organism; members of a population who share
similar characteristics
-population: group of individuals of a particular species that live in the
same area
-tropical rainforests have the most biodiversity
Speciation
-speciation: the process by which new species are generated
-allopatric speciation: species formation due to the physical separation of
populations over some geographical distance
-mutations in a population separated from others of its species create a
new species
-speciation allows single species to generate multiple species, each of
which can then generate more
-sympatric speciation: when species form from populations that become
reproductively isolated within the same geographical area
Population Separation
-through allopatric speciation:
+glacial ice sheets move across continents and split
+mountain ranges rise and separate organisms
+drying climates evaporate bodies of water, separating them into
multiple bodies of water
+warming/cooling temperatures cause plant populations to move
up/down a slope
+for speciation to occur, populations must remain separated for a
long time
+if the isolation process reverses itself, the species can come back
together. if species have changed enough, they will not interbreed and
two new species will have formed. if they were not separated long
enough, they will continue to breed and exchange mutations.
-through sympatric speciation:
+species of insects feed and mate exclusively on different types of
plants
+mate during different seasons
+mutations have changed the number of chromosomes in plants
Extinction
-human impact can greatly affect the rate at which extinction occurs
-extinction helps determine biodiversity
-extinction usually occurs when environmental conditions change rapidly
or severely enough that a species cannot adapt genetically
-small populations and species dependent on a resource/way of life are
the most vulnerable to extinction
-endemic: occurring nowhere else in the world
+endemic species are incredibly vulnerable
+all members belong to one, often small population
+in the US, many amphibians are endemic
-background extinction rate: the rate at which gradual extinction occurs
-mass extinction events: events that kill off massive numbers of species
at one time
+Earth has seen five so far
*most well-known: end of dinosaurs (K-T event)
+sixth mass extinction is allegedly upon us
*caused by humans
*alteration and destruction of habitats
Levels of Ecology
-biosphere: the cumulative total of living things on Earth and the areas
they inhabit
-ecologists study relationships mainly on the organismal, community, and
ecosystem levels
-community: multiple interacting species that live in the same area
-ecosystem: multiple communities and the abiotic material and forces
with which their members interact
-ecology describes the relationships between organisms and their physical
environments
-population ecology studies how individuals within a species react with
each other
+helps explain why some populations decrease while others increase
-community ecology studies interactions among species
-ecosystem ecology reveals patterns, such as energy and nutrient low, by
studying living and nonliving components of systems in conjunction
-organismal ecology studies how each organism relates to its environment
+each organism tries to maximize its survival and reproduction
+habitat, niche, and specialization are important to organismal
ecology
*habitat is the environment in which an organism lives
~mobile organisms select habitats in which to live through
habitat selection; only choose those which meet their criteria
~availability of a habitat is crucial to an organism's wellbeing and survival
*niche is an organism's use of resources and its functional role
in a community
~includes habitat use, consumption, interactions
~summary of everything an organism does and how it
affects others in the community
+specialists are organisms that have very specific requirements that
must be met
*can be successful over time by being good at what they do, but
are vulnerable to extinction
+generalists are organisms that have a broad set of requirements
they will tolerate
*succeed by being very adaptable
*may not thrive in any one habitat as a specialist does
Population Ecology
-population density: the number of individuals within one population per
unit area
+larger organisms generally have lower population density because
they require more resources
+high population density can make it easier to find mates, but can
lead to food/space conflicts or spread of disease
-population distribution: the spatial arrangement of organisms within an
area
+three types: random, uniform, clumped (see notes for more info)
-sex ratio: proportion of males to females
+50/50 sex ratio in species who only take one mate is ideal for
population growth
-age distribution: relative numbers of organisms of each age within a
population
+age pyramids or age structure diagrams are often used to visual age
distribution
-crude birth/death rate: the measurement of the number of
births/deaths per 1,000 individuals in a given time period
+some species have high death rates and high birth rates because
offspring die young
+survivorship curves show how likelihood of death varies with age
*three fundamental types:
=type 1: high death rate at older ages (ex: humans)
=type 2: equal rates of death at all ages (ex: many birds)
=type 3: high death rate at younger ages (ex: toads)
-population growth or decline is determined by four factors:
+natality: births within the population
+mortality: deaths within the population
+immigration: arrival of individuals from outside the population
+emigration: departure of individuals form within the population
-equation for growth rate:
+ (crude birth rate + immigration rate) - (crude death rate +
emigration rate) = growth rate
+tells net change in population size per 1,000 individuals
+multiply growth rate by 100 to find percentage of growth
Population Growth
-limiting factors: physical, chemical, and biological characteristics of an
environment that restrain population growth
-density-dependent factors: influence is affected by population density;
ex: ability to find a mate
-density-independent factors: limiting factors whose influence is not
affected by pop density; ex: natural disasters
-biotic potential: ability to produce offspring