Read the article and write 2 pages essay including few deatils from the chapters which are attacged below.

Lecture Outlines

Withgott | Laposata

Sixth Edition

ENVIRONMENT the science behind the stories

Chapter 3

Evolution, Biodiversity, and Population Ecology

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Lecture objectives  Explain natural selection with evidence.  Describe how evolution influences biodiversity.  Discuss the causes of species extinctions, including

significant mass extinction events.  List the levels of ecological organization.  Predict the growth of a population based on its

characteristics.  Assess a population’s logistic growth, carrying

capacity, and limiting factors.  Identify efforts and challenges in biodiversity

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 Hawaii’s geographic isolation in the middle of the Pacific Ocean has created a cradle of evolution.

 Half of the native bird species have gone extinct since the 18th century, primarily due to human influences.

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 The aki is one of 18 living species of Hawaiian honeycreepers that diverged from a single ancestral species that reached Hawaii millions of years ago.  Each species has its own set of unique

characteristics, such as bill shape.

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 The aki has a distinctly curved bill that it uses to get nectar from a similarly shaped flower.

 Hawaiian forests are under siege due to clearcutting and non-native species introduction first by Polynesian settlers, then European settlers.

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Evolution: The Source of Earth’s Biodiversity  A species is a classification of organism whose

members can interbreed and produce fertile offspring.

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 A population is a group of individuals within a species that live in the same geographic area.

 Populations change over multiple generations as genetic changes alter their physical and behavioral characteristics, a process called evolution.  Evolution originates in genes and often leads to

modifications in appearance or behavior.

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Natural selection shapes organisms  Evolution is driven by natural selection, a process

that favors certain inherited characteristics over others, causing them to be passed on more frequently.

 The idea of natural selection is based on three observations:  Organisms face a constant struggle to survive and

reproduce.  Organisms tend to produce more offspring than can

survive to maturity.  Individuals of a species vary in their attributes.

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 The concept of natural selection was first proposed in the 1850s by Charles Darwin and, independently by Alfred Russel Wallace, two British naturalists.

 Attributes are passed from parent to offspring through genes.  Genes that lead to better reproductive success will

eventually evolve through the entire population. This is called adaptation.

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Selection acts on genetic variation  Accidental changes in DNA, called mutations, give

rise to genetic variation in individuals.  The mixing of genetic material through sexual

reproduction also generates variation.  Natural selection can drive a feature in a particular

direction.

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 The average bill length of the ‘i’iwi can shift depending on the environment.  An environment with flowers

with short nectar tubes would favor short beaks.  An environment with flowers

with long nectar tubes would favor long beaks.

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Selective pressures from the environment influence adaptation  Closely related species that live in different

environments tend to diverge in their traits.  Different selective pressure → different adaptations

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 Unrelated species living in similar environments in separate locations may independently acquire similar traits.  Similar selective pressures.  This is called convergent

evolution.

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Evidence of selection is all around us  Humans have conducted selection under our own

direction, called artificial selection.  Domesticated dogs, cats, and livestock

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Understanding evolution is vital for modern society  Many medical advances have resulted from our

knowledge of evolution.  How infectious diseases spread and gain or lose

potency.  Tracking evolving strains of influenza, HIV, and other

pathogens.  Detection of the evolution of antibiotic resistance in

bacteria.

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Evolution generates biodiversity  Biological diversity, or biodiversity, refers to the

variety of life across all levels.  Species, genes, populations, and communities

 About 1.8 million species have been identified, but the actual amount may be 3–100 million.

 The process by which new species are generated is termed speciation.

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Speciation produces new types of organisms  Allopatric speciation occurs when

populations become physically separated over a geographic distance.

 When a mutation arises in an organism of one of the populations, it does not spread to the other.  Eventually the populations grow so

different that they can no longer mate.

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We can infer the history of life’s diversification by comparing organisms  Scientists represent the

history of divergence with phylogenetic trees.  Constructed by analyzing

genes and external traits of organisms

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 Taxonomists group species into categories meant to reflect evolutionary relationships.  Related species are grouped into a genus, related

genera are grouped into families, etc.

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Fossils reveal life’s long history  A fossil is an imprint in stone of a dead organism.  By dating the rock layers that

contain fossils, paleontologists can learn when the organisms lived.  The body of fossils worldwide

is called the fossil record.  The vast majority of species

that once lived have disappeared due to extinction.

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Some species are especially vulnerable to extinction  Extinction occurs when the

environment changes more rapidly than the species can adapt.

 Small and narrowly specialized populations are the most vulnerable.  For example, Hawaii’s native

birds and plants did not evolve defenses against mammal predators.

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 Species that are endemic to a region, meaning they occur nowhere else on the planet, are especially vulnerable.  If an event affects their region, it affects all members

of the species.  Island-dwelling species are also at elevated risk of

extinction, because many have been isolated from typical evolutionary pressures, such as the presence of predators.

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Earth has seen several episodes of mass extinction  Most extinction happens gradually, at a rate called

the background extinction rate.  The Earth has seen at least five mass extinction

events that wiped out 50–95% of Earth’s species each time.  The most catastrophic was the Permian extinction,

250 million years ago.  Causes can include volcanism, asteroid impact,

methane releases, and global warming.

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 Today’s extinction rate is 100–1000 times higher than the background rate, and rising.

 Causes stem from human population growth:  Altering or destroying natural habitats  Overhunting and overharvesting  Pollution of air, water, and soil  Introduction of non-native species  Climate change

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Review Questions 1. Broccoli is a type of vegetable created by human

farmers by breeding wild mustard plants for large flower buds and stems. Both are the same species, Brassica oleracea. What is this an example of? a. Speciation b. Artificial selection c. Natural selection d. Background extinction

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Review Questions 2. Which of these is an accurate statement regarding

extinction? a. Most extinctions have occurred due to catastrophic

natural disasters. b. Species are currently going extinct at a level

significantly below the background rate. c. Species are currently going extinct at a level

significantly greater than the background rate. d. The fossil record only contains evidence of a single

mass extinction event.

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Ecology and the Organism  Ecology is the study of the interactions among

organisms and with their environments, and includes many levels.

 The organism, a single living thing

 A population, or group of individuals of the same species that live in the same area

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 A community includes all of the populations of species that live and interact within an area.  Community ecology studies these interactions.

 Ecosystems include communities and all of the abiotic, or nonliving parts of the environment.  Ecosystem ecology studies the flow of energy

and nutrients between the living and nonliving parts.

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 The biosphere is the sum total of all living things and habitats on the Earth.  Landscape ecology examines how ecosystems,

communities, and populations are distributed across the Earth.

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Each organism has habitat needs  Each organism has a relationship with its habitat,

the environment in which it lives.  Rock, soil, leaf litter, plant life, etc.  Depending on the species, a habitat may be a square

meter of soil, or many miles of land.  Organisms thrive in certain habitats and not others,

creating patterns of habitat use.  Mobile organisms are able to choose where they

live, a process called habitat selection.

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Organisms have roles in communities  An organism’s role in its community is its niche.  Includes resource use and interaction with other

organisms  Species with narrow niches are specialists.  The ‘akiapōlā’au

specializes in digging grubs out of trees.

 Species that can utilize a wider variety of resources are generalists.

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Population Ecology  Population size, the number of organisms in an

area at a given time, will grow when resources are abundant and natural enemies are few.  Declines due to resource

loss, natural disaster, or impacts from other species  The North American

passenger pigeon declined and went extinct due to overhunting.

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 Population density describes the number of individuals per unit area.

 Population distribution describes the spatial arrangement of organisms within an area.  Random distribution shows no particular pattern.  Uniform distribution has individuals spaced evenly.  Clumped distribution occurs when individuals

concentrate in certain areas.

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 Sex ratio is the proportion of males to females.  1:1 ratios are seen in monogamous species; ratios

vary in others.  Age structure describes the number of individuals

of different ages within a population.  This can help to predict whether a population will

grow or shrink in the near future.

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Populations may grow, shrink, or remain stable  Demographers, scientists who study population

change, track the four key population factors:  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.  A population’s rate of natural increase is

determined by subtracting the death rate from the birth rate.

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 The actual population growth rate includes the effects of emigration and immigration:

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

 Rates may be expressed per 1000 individuals per year. These can be used in the formula.

 Growth rates may be expressed as percentages: population growth rate x 100%

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Unregulated populations increase by exponential growth  When a population increases by a fixed percentage

each year, it undergoes exponential growth.  When graphed, these populations produce a

J-shaped curve.  Exponential growth only

occurs in nature when a population is small, competition is minimal, and environmental conditions are ideal.

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Limiting factors restrain growth  Eventually, every population is constrained by

physical, chemical, and biological limiting factors in the environment.  These factors determine carrying capacity, the

maximum population size of a species that an environment can sustain.

 Population growth slows as it reaches the carrying capacity. This produces an S-shaped curve called logistic growth.

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 The Eurasian collared dove is a non-native species that has reached carrying capacity in Florida, where it was introduced.  In other areas, its population grows slowly or

exponentially, depending on how recently it arrived.

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The influence of some factors depends on population density  The density of a population can enhance or diminish

the effect of some limiting factors.  Density-dependent factors rise and fall with

population density.  Predation, disease

 Density-independent factors are unaffected by population density.  Temperature extremes, catastrophic natural disasters

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Life history strategies vary among species  The life history theory explains how natural

selection influences reproduction, survival and lifespan.  Differences in how species invest in reproduction,

parental care, and survival are depicted in survivorship curves.

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 Type III survivorship curves occur when species produce many offspring, but do not care for them.  Survival is due to chance.  These are also called r-selected species, and do well

in changing and unpredictable environments.

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 Type I survivorship curves are observed in species that have few offspring, but invest heavily in their survival.  These are also called K-selected species, and are

found in stable environments.

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Conserving Biodiversity  Human development and resource extraction are

speeding the natural rate of environmental change that affects populations.  One example is introduced species, which displace or

kill native species.

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Innovative solutions are working  A wide variety of organizations work to protect land,

remove alien species, and restore native habitats.  These efforts can create economic benefits, as

visitors are drawn to wildlife and natural areas.  This is called ecotourism.  Hawaii’s economy takes

in $12 billion annually from more than 7 million visitors per year.

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Climate change poses an extra challenge  As temperatures and rainfall patterns change, even

protected areas may be affected.  The mountainous Hakalau Forest in Hawai’i is

predicted to experience an increase in the range of malaria-carrying mosquitoes.

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Review Questions 3. Which is a true statement about this graph?

a. This species is undergoing exponential growth. b. Limiting factors are present for this species. c. The carrying capacity for this species is apparent. d. This is an example of a Type III survivorship curve.

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