Download Ch. 5: Evolution, Biodiversity & Population Ecology

Chapter 5: Evolution, Biodiversity
& Population Ecology
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Evolution
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genetic change in populations of organisms
across generations.
modifications
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appearance:
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Evolution
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functioning: beaks in honeycreepers
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Natural Selection
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explains the great variety of living organisms.
derives from several premises noticed in
nature
Natural Selection Premises
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constant struggle of organisms to survive
and mate
organisms tend to produce more offspring
that can survive.
individuals of the same species are not
identical
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variation
Variation
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genetical differences
environment within which genes are
expressed
interaction between genes and environment
Adaptation: trait that promotes success of a
species
Effects of Natural Selection on Genetic
Variation
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Mutations: accidental changes in the
nucleotide sequence of the DNA
addition
deletion
substitution
Sexual Reproduction also Generates
Variation
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recombination of genes produces a novel
combination generating variation
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directional selection
stabilizing selection
disruptive selection
Directional selection
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selection that drives a feature in one
direction
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Stabilizing selection
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preserves status quo, no changes
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Disruptive Selection
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traits diverge into two or more directions
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Evidence of Natural Selection
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Selective breeding
breeding of domesticated animals and plants
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dog and cat breeds
variations of Brassica oleracea
artificial selection
Biodiversity
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Total of all organisms in the area
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Evolution generates biological diversity
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diversity of species
gene pool
populations
communities
as of 2008 1:3 amphibians, 1:7 birds and 1:5 mammals is
considered endangered or threaten (National Geographic)
Species: organism that is able to reproduce and
have viable offspring
Speciation: Allopatric & Sympatric
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Allopatric: species form due to physical
separation
mutations can occur independently
members of different populations don't mate
populations continue diverging through time
single species can generate multiple species
through time
Separation of Populations
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glacial ice sheets during ice ages
change of course of major rivers
rise of mountain ranges
evaporation of major lakes into smaller bodies of water
temperature variation causing migration of plant populations
creating new patterns of animal/plant distribution
isolation must remain for thousands of generations
reunion of populations may occur, but if they are not able to
interbreed, two or more new species have emerged.
Sympatric
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reproductively isolated due to behavioral
causes
feeding at different times of the day
feed at different sites
mating on different times of the year
hybridization in some plants
mutations causing change in number of
chromosomes
Diversification
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as a result of numerous speciation events
phylogenetic trees explain differences and
similarities between species
Speciation and extinction
natural process that takes 1-10 million years
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Diversification
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Species Vulnerable to Extinction
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some species may be more vulnerable than others
due to change in environmental conditions
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climate change
rise and fall of sea level
arrival of harmful species
extreme weather events (drought, flood, etc.)
Endemic: single small population present only in a
particular type of environment: Attwater chicken
Attwater Chicken
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1 million individuals in 1900
50 or so individuals today
habitat disruption
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oil industry, housing, cattle, rice
fields
predators (snake, rat, skunk)
diseases
weather
collision (fence, cars)
fire ants (kill chicks)
Levels of Ecological Organization
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Species
Population
Communities
Ecosystems
Biosphere
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Ecological Organization
Habitat, Niche and Specialization
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Habitat: living and non-living elements
around a species
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thriving of a species depends on patterns of
habitat use
each species' habitat is scale dependent
habitat selection is possible if the species is
mobile
the survival of the species depends if the habitat
is suitable or not
Niche
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a species' niche reflects its use of resources and
functional role in the ecosystem
"job"
specialists and generalists
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Prairie dog
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eats grasses and keeps grass low for predator control
more grass grown around burrow because
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airiates soil by digging
soil becomes richer near burrows because of dung
burrow houses other animals when empty (snakes, rabbits,
owls)
Population Ecology
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Population size: number of individuals present at a
given time
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Population density: number of individuals per
population per unit area
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Attwater chicken- 1 million to 50 individuals
golden toad- large population in a small area
Population distribution: spatial arrangement of
organisms within an area. There are 3 types.
Population Distribution: Random
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Uniform
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Clumped
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Population Ecology
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sex ratio: depends on the behavior (monogamous or
polygamous) of the species, type of reproduction
(autofecundates or different sexes)
age structure: age structure diagrams
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Population Ecology
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birth and death rates: survivorship curves
– type I: higher mortality at older age
– type II: equal rate of death at any age
– type III: higher rate of death at younger age
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k-selected
r-selected
Population Ecology
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Immigration
emigration
growth rate
Unregulated population increase: shows exponential
growth= J curve
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carrying capacity causes logistic growth curve (S curve) to
show
caused by an environmental resistance (water, food, shelter,
predators, disease)
Density-dependent factors
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its influence is affected by the population
density
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competition
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food
shelter
mate
water
s-shaped curve
Density-independent factors
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influence is not affected by population
density; can eliminate large numbers of
individuals without regard to its density
extreme temperatures
catastrophic climate events
fires
volcano eruptions
Biotic Potential vs Reproductive
Strategy
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k-selected (k stands for Carrying capacity)
low biotic potential
long gestation period
protects offspring as an investment for
species survivor
relative few offspring during lifetime
type 1 curve
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eg: humans, whale, rhino, elephant
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r-selected (r stands for rate)
focus on quantity not quality
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high biotic potential
large number of offspring
survivor of offspring depends on chance
type 3 curve
eg. fish, frogs, snails
Conservation of Biodiversity
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social and economic factors
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human behavior towards environment
economy vs environmental protection
protection of environment
began without much government support
– even today governments may not have the funds
– ecotourism is the key
THE END
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