SBS 4e Lecture Ch03 PC

7/29/2019 SBS 4e Lecture Ch03 PC

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2011 Pearson Education, Inc.

Lecture Outlines

Chapter 3

Environment:The Science behind the

Stories

4th Edition

Withgott/Brennan


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This lecture will help you understand:

Natural selection How evolution influences

biodiversity

Reasons for speciesextinction

Ecological organization

Population characteristics

Population ecology

Conserving biodiversity


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Striking gold in Costa Rica

In 1964, Golden toads were

discovered in Monteverde,Costa Rica

The mountainous cloud

forest has a perfect climatefor amphibians

They became extinct within25 years

- Climate changes dryingeffect on the forest

- A lethal fungus


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Evolution generates biodiversity

Species = a population or group of populations

- Whose members share characteristics

- They can breed with one another and producefertile offspring

Population = a group of individuals of a species thatlive in the same area

Evolution = means change over time

- Biological evolution: genetic change inpopulations over time

- Genetic changes lead to changes in appearance,

functioning or behavior over generations


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Natural selection

Evolution may be random

- Or directed by natural selection

Natural Selection = traits that enhance survival andreproduction

- Are passed on more frequently to future generations- Than those that do not


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Evolution by natural selection

It is one of the best-supported and most illuminating

concepts in all science

It is the standpoint of modern biology

We must understand it to appreciate environmental

science

Knowing ecology and learning the history of life

Evolutionary processes influence pesticide

resistance, agriculture, medicine, health, etc.

In 1858, both Darwin and Wallace proposed natural

selection as the mechanism of evolution


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Natural selection shapes organisms

Premises of natural selection:

- Organisms struggle to survive and reproduce

- Organisms produce more offspring than can

survive

- Individuals of a species vary in theircharacteristics due to genes and the environment

- Some individuals are better suited to theirenvironment and reproduce more effectively

Natural selection acts on genetic variation



Genetic variation

Adaptation = the process where, over time,

characteristics (traits) that lead to better reproductivesuccess

- Become more prevalent in the population

Adaptive trait (adaptation) = a trait that promotesreproductive success

Mutations = accidental changes in DNA that may bepassed on to the next generation

- Non-lethal mutations provide the genetic variation onwhich natural selection acts

Sexual reproduction also leads to variation



Natural selection acts on genetic variation

Natural selection changes

characteristics through:

Directional selection =drives a feature in onedirection

Stabilizing selection =favors intermediate traits

- Preserving the status quo

Disruptive selection = traitsdiverge in two or moredirections



Environmental conditions affect selection

Environmental conditions determine the pressures naturalselection exerts

- These pressures affect who survives and reproduces

- Traits evolve that allow success in that environment But traits that promote success at one time or place may

not do so at another

Natural selection weeds out unfit individuals

- It also elaborates and diversifies traits that mayproduce new species



Selective pressures influence adaptation

Related species in

different environments- Experience different

pressures

- Evolve different traits

Convergent evolution =

unrelated species mayevolve similar traits

- Because they live insimilar environments



Evidence of natural selection is everywhere

It is evident in every adaptation of every organism

Artificial Selection = the process of selectionconducted under human direction

- Producing the great variety of dog breeds and foodcrops



Evolution generates biological diversity

Biological diversity (biodiversity) = the variety of lifeacross all levels of biological organization

- Species

- Genes

- Populations

- Communities

Scientists have described 1.8 million species

- Up to 100 million species may exist

- Tropical rainforests are rich in biodiversity



Speciation produces new types of organisms

The process of generating new

species from a single species

Allopatric speciation: speciesformation due to physical

separation of populations- The main mode of speciation

- Populations can be separatedby glaciers, rivers, mountains

- Each population gets its ownset of mutations



Another type of speciation

Sympatric speciation = species form from populationsthat become reproductively isolated within the same area

- Feed in different areas- Mate in different seasons

- Hybridization between two species

- Mutations


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Speciation results in diverse life forms

How do major groups diverge over time?

Phylogenetic trees (cladograms) = showrelationships among species, groups, genes, etc.

- Scientists can trace how certain traits evolved


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The fossil record

Fossil: an imprint in stone of a dead organism

Fossil record: the cumulative body of fossils worldwide

The fossil record shows:

- Life has existed on Earth for at least 3.5 billion years

- Earlier types of organisms evolved into later ones

- The number of species has increased over time

- Most species have gone extinct

- There have been several mass extinctions in the past


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Extinction

Extinction = the disappearanceof a species from Earth

- Species last 1-10 millionyears

Biological diversity is nowbeing lost at an astounding rate

- This loss of species is

irreversible

Number of species = speciation - extinction


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Extinction is a natural process, but

Humans profoundly affect rates of extinction Biodiversity loss affects people directly

- Food, fiber, medicine, ecosystem services


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Some species are more vulnerable to

extinction

Extinction occurs when the environment changes rapidly

- Natural selection can not keep up

Many factors cause extinction:

- Severe weather, climate change, changing sea levels

- New species, small populations

- Specialized species

Endemic species = a species only exists in a certain,specialized area

- Very susceptible to extinction

- These species usually have small populations


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Many U.S. amphibian species are vulnerable

Many U.S. amphibians have very small ranges

- They are vulnerable to extinction- The Yosemite toad, Houston toad, Florida bog frog

40 salamander species are restricted to areas the size of

a typical county

Some U.S. salamander species live on top of single mountains


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Earth has had several mass extinctions

Background extinction rate = extinction usually occurs

one species at a time

Mass extinction events = killed off massive numbers

of species at once- Occurred five times in Earths history

- 50-95% of all species went extinct at one time

Cretaceous-Tertiary (K-T) event: 65 million years ago

- Dinosaurs went extinct End-Permian event: 250 million years ago

- 75-95% of all species went extinct


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The sixth mass extinction is upon us

Humans are causing the sixth mass extinction event- Resource depletion, population growth, development

- Destruction of natural habitats

- Hunting and harvesting of species

- Introduction of non-native species

It is 100-1,000 times higher than the background rate and

rising

Amphibians are disappearing the fastest- 170 species have already vanished

It will take millions of years for life to recover


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The geologic record


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Macroevolution


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Ecology is studied at several levels

Ecology and evolution are

tightly intertwined

Biosphere = the total livingthings on Earth

- And the areas they inhabit

Community = interactingspecies living in the samearea

Ecosystem = communitiesand the nonliving materialand forces they interact with


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Levels of ecological studies

Population ecology = investigates the dynamics ofpopulation change

- The factors affecting the distribution and abundance ofmembers of a population

- Why some populations increase and others decrease

Community ecology = focuses on patterns of speciesdiversity and interactions

Ecosystem ecology = studies living and nonlivingcomponents of systems to reveal patterns

- Nutrient and energy flows


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Each organism has habitat needs

Habitat = the environment where an organism lives- It includes living and nonliving elements

Habitat use = each organism thrives in certainhabitats, but not in others

- Results in nonrandom patterns of use

Habitat selection = the process by which organismsactively select habitats in which to live

- Availability and quality of habitat are crucial to anorganisms well-being

- Human developments conflict with this process


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A specialized frog

Epiphytes grow on trees for support- Obtaining water from the air

- They collect pools of rainwater and pockets of leaflitter

- Frogs lay their eggs inthese rainwater pools


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Habitats vary

Habitats vary with the body size and needs of species

- A soil mite vs. an elephant

Species have different habitat needs at different times

- Migratory birds use different habitats duringmigration, summer and winter

Species use different criteria to select habitat

- Soil, topography, vegetation, other species

- Water temperature, salinity, prey

Species survival depends on having suitable habitat


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Organismal ecology: niche

Niche = an organisms use of resources- Along with its functional role in a community

- Habitat use, food selection, role in energy and

nutrient flow, interactions with other individuals

Specialists = have narrow niches and specific needs

- Extremely good at what they do

- But vulnerable when conditions change

Generalists = species with broad niches

- They use a wide array of habitats and resources

- They can live in many different places


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All populations showcharacteristics that helpscientists predict theirfuture dynamics

Population size = thenumber of individualorganisms present at agiven time

- Numbers can increase,decrease, cycle orremain the same


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Population density = the number of individuals in apopulation per unit area

Large organisms usually have low densities

- They need many resources and a large area to survive

High densities make it easier to find mates

- But increase competition and vulnerability to predation

- Increased transmission of diseases

Low densities make it harder to find mates- But individuals enjoy plentiful resources and space


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Population distribution(dispersion) = spatialarrangement of organisms

Random = haphazardly located

individuals, with no pattern Uniform = individuals are

evenly spaced

- Territoriality, competition

Clumped= arranged accordingto availability of resources

- Most common in nature


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Sex ratio = proportion of males to females

- In monogamous species, a 1:1 sex ratio maximizespopulation growth

Age distribution (structure) = the relative numbers

of organisms of each age in a population- Age structure diagrams (pyramids) = show the age

structure of populations

In species that continue growing as they age

- Older individuals reproduce more (i.e. a tree)

- Experience makes older individuals better breeders



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Birth and death rates

Type I: more deaths at olderages

Type II: equal number ofdeaths at all ages

Type III: more deaths at

young ages

Survivorship curves = the likelihood of death varies with

age

F f f l i h


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Four factors of population change

Natality = births within the population Mortality = deaths within the population

Immigration = arrival of individuals from outside the

population Emigration = departure of individuals from the

population

Births and immigration add individuals

- Deaths and emigration remove individuals

Crude birth (death) rates: number of births (deaths) per1000 individuals per year

P l i h


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Population growth rate

Natural rate of population growth =

(Crude birth rate)(crude death rate)

- Population change due to internal factors

Population growth rate =

(Crude birth rate + immigration rate)(Crude death rate+ emigration rate)

- Net changes in a populations size/1000/year

Growth rate as a percent =

- Population growth rate * 100%

- Populations of different sizes can be compared

E ti l l ti th


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Exponential population growth

Exponential growth

- A population increases by afixed percent

- Graphed as a J-shaped

curve Exponential growth cannot

be sustained indefinitely

It occurs in nature with a:

- Small population- Low competition

- Ideal conditions


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Limiting factors restrain population growth

Limiting factors = physical, chemical and biologicalattributes of the environment

- They restrain population growth

Environmental resistance = all limiting factors takentogether

- Stabilizes the population size

- Space, food, water, mates, shelter, suitable breedingsites, temperature, disease, predators

- Aquatic systems: salinity, sunlight, temperature, etc.

C i it


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Carrying capacity

Carrying capacity = themaximum population sizeof a species that itsenvironment can sustain

Limiting factors slow andstop exponential growth

- An S-shaped logisticgrowth curve

Many factors contribute to environmental resistance and

influence a populations growth rate and carrying capacity

P l ti d it i t li iti f t


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Population density impacts limiting factors

Density-dependent factors = limiting factors whoseinfluence is affected by population density

- Increased density increases the risk of predation andcompetition for mates

- Results in the logistic growth curve

- Larger populations have stronger environmentalresistance

Density-independent factors = limiting factors whoseinfluence is not affected by population density

- Events such as floods, fires, and landslides

P f t l i ti t ft f d


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Perfect logistic curves arent often found

C i iti h


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Carrying capacities can change

Environments are complex and ever-changing

- Changing carrying capacities

Humans lower environmental resistance for themselves

- Increasing our carrying capacity- Technologies overcome limiting factors

By increasing carrying capacity for humans

- We have reduced the carrying capacity for countlessother organisms

- Calling into question our own long-term survival


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Reproductive strategies vary among species

Biotic potential = an organisms capacity to produceoffspring

K-selected species = species with long gestation periodsand few offspring

- Have a low biotic potential

- Stabilize at or near carrying capacity

- Good competitors

r-selected species = species which reproduce quickly

- Have a high biotic potential

- Little parental care, populations fluctuate greatly


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Population changes affect communities

As the population of one species declines, other speciesmay appear

Human development displaces other species and threatensbiodiversity

As Monteverde dried out, species disappeared

- Golden toads, harlequin frogs and more had beenpushed from their cloud-forest habitat into extinction

- 20 of 50 frog species, 2 lizard species went extinct Species from lower, drier habitats appeared

- 15 species tolerant of drier conditions had moved in



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Human development, resource extraction andpopulation pressure are speeding changes

- In populations and communities

Impacts threatening biodiversity have complex social,

economic and political roots

- We must understand these factors to solve problems

Costa Rica and its environment


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Costa Rica and its environment

Past economic and social forces still threaten CostaRicas species and ecological communities

- Lush forests are seen as obstacles to agriculture and for

timber- The countrys population grew to 3.34 million

- Pasture land increased from 12% to 33%

- Forests decreased from 80% to 25%- Species were declining and becoming endangered

Costa Ricas species were in danger


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Costa Ricas species were in danger

Few people saw the need to conserve biological resources

- Until it became clear they were being rapidly lost

Costa Rica is protecting its environment


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Costa Rica is protecting its environment

The privately managed 10,500 ha (26,000 acre)

Monteverde Cloud Forest Reserve was founded in 1972

- To protect the forest, its plants and animals

Costa Rica created the countrys first national parks and

protected areas in 1970- Centered on areas of spectacular scenery

- Protecting valuable tropical dry forests, turtle nesting

beaches, coral reef systems Government support remains strong

- Over 25% of its land is under some type of protection

Costa Ricos protection is paying off


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Costa Rico s protection is paying off

Ecotourism: tourists visit protected areas

- Providing thousands of jobs and billions of dollarsto local economies

But parks are still under-protected and underfunded

- Restoration is a step beyond preservation

Conclusion


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Conclusion

The fundamentals of evolution and population ecologyare integral to environmental science

Natural selection, speciation and extinction helpdetermine earths biodiversity

Understanding how ecological processes function at thepopulation level is crucial to protecting biodiversity

QUESTION: Review


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QUESTION: Review

Which of the following is NOT a part of the process ofnatural selection?

a) Once grown, organisms generally dont have tostruggle to survive

b) Organisms produce more young than can survive

c) Individuals vary in their genetic characteristics

d) Some individuals are better suited to their

environment than others

QUESTION: Review


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QUESTION: Review

What happens as a result of adaptation?

a) Species have lower reproductive success and lowersurvival.

b) Species have higher reproductive success and higher

survival.c) Species have higher reproductive success and lower

survival.

d) Species have lower reproductive success and highersurvival.

QUESTION: Review


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QUESTION: Review

Directional selection would result in which of the

following?

a) Dogs with black coats evolving whiter coats in colderareas

b) Red and white flowers interbreeding, producing pinkflowers

c) Fish evolving bigger eyes as the water gets muddier

d) A population of birds, some with thicker beaks thateat seeds, and others with thinner beaks that eatinsects

QUESTION: Review


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QUESTION: Review

Allopatric speciation would occur in:

a) One population that mates in May, and another thatmates in June

b) Two populations separated by the Mississippi River

c) One population that feeds in tree branches, anotherfeeds on tree trunks

d) A population with a mutation that turns fur a differentcolor than usual

QUESTION: Review


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QUESTION: Review

Which of these species is MOST vulnerable to extinction?

a) A species with a population size of 500 individuals

b) A species distributed in one county of the United

Statesc) A species that eats many different plant species

d) A species that has hundreds of offspring

QUESTION: Review


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QUESTION: Review

A community is defined as:

a) The total of living things on Earth

b) Members of the same population that can interbreed

c) Interacting species in an area

d) Species and the nonliving material they interact with

QUESTION: Viewpoints


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Should we care whether a species goes extinct?

a) Yes, because all life is important and valuable.

b) Yes, because we are causing this wave of

extinction, so we should fix it.c) We should not, because its natural.

d) I dont care; it really does not affect me.



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Do you think humans are subject to limiting factors and,ultimately, a fixed carrying capacity?

a) Yes, although we have raised the carrying capacity,there are limits to the number of humans Earth cansupport.

b) Yes, but technology will keep raising the carryingcapacity, so its not much of a problem.

c) No, humans are no longer constrained byenvironmental limits, due to our technology andability to manipulate the environment.

d) I dont care; it really does not affect me.

QUESTION: Interpreting Graphs and Data


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Which type of distribution is a

result of competition betweenindividuals?

a) Random

b) Uniform

c) Clumped

d) None of these



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What does this graph

show?a) The effects of

carrying capacity onpopulation growth

b) A population thatkeeps growing

c) The effects ofexponential growth

d) The effects ofincreasing carryingcapacity

SBS 4e Lecture Ch03 PC

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