GEOG1000 Chapter 3 Evolution, Biodiversity and Population Ecology.pdf

Essential Environment Chapter 3- Evolution, Biodiversity and Population Ecology

1. Essential
Environment
Chapter 3
Evolution, biodiversity &
population ecology
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2. This lecture
will help you
understand:
Natural selection
How evolution influences biodiversity
Reasons for species extinction
Ecological organization
Population characteristics
Population ecology
Conserving biodiversity

3. I. Evolution
THE SOURCE OF EARTH’S BIODIVERSITY
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4. Central Case Study:
Saving Hawaii’s Native Forest Birds
▪Evolution in the Hawaiian Islands has generated
hundreds of species, many unique to the islands
▪The island chain was once home to 140 species of native
birds
▪In recent times, half of the native bird species have gone
extinct
▪Introduced species (like pigs, cattle, rats, and cats)
destroyed habitat and killed eggs and young
▪Avian malaria killed native birds at lower elevations

7. Evolution: The Source of Earth’s Biodiversity
▪Species=a population or group of populations whose
members share characteristics
▪They can breed with one another and produce fertile
offspring
▪Population=a group of individuals of a species that live in
the same area
▪Evolution=change over time
▪Biological evolution=change in populations of organisms
over generations
▪Genetic changes lead to changes in appearance,
functioning, or behavior

8. Evolution: The Source of Earth’s Biodiversity
▪Genetic changes in evolution may be random
▪But may be directed by natural selection
▪Natural selection=process in which traits that
enhance survival and reproduction are passed
on more frequently to future generations than
those that do not
▪Genetic makeup of future populations is
changed

9. Hawai’i Biodiversity

10. Evolution: The Source of Earth’s Biodiversity
▪Evolution is one of the best-supported and most
illuminating concepts in all science
▪It is the foundation of modern biology
▪We must understand it to appreciate environmental
science
▪Understanding how species change over time and
adapt to their surroundings is crucial for
comprehending ecology and the history of life
▪Evolutionary processes influence pesticide resistance,
agriculture, medicine, health, etc.

11. Natural selection shapes organisms and
diversity
▪In 1858, both Darwin and Wallace proposed natural selection as the
mechanism of evolution
▪Premises of natural selection:
▪Organisms struggle to survive and reproduce
▪Organisms produce more offspring than can survive
▪Individuals of a species vary in their characteristics due to genes
and the environment
▪Some individuals are better suited to their environment and
reproduce more effectively
▪Organisms with better adapted traits will produce more offspring

12. Natural selection shapes organisms and
diversity
▪Adaptation=the process where, over time,
characteristics (traits) that lead to better reproductive
success become more prevalent in the population
▪Adaptive trait (adaptation)=a trait that promotes
reproductive success
▪Mutations=accidental changes in DNA that may be
passed on to the next generation
▪Non-lethal mutations provide the genetic variation
on which natural selection acts
▪Sexual reproduction also leads to variation
▪Directional selection=drives a feature in one direction

14. Selective pressures from the environment
influence adaptation
▪Related species in different environments
experience different pressures and evolve
different traits
▪Convergent evolution=unrelated species may
acquire similar traits because they live in similar
environments

16. Evidence of
natural
selection is
all around us
▪It is evident in every adaptation
of every organism
▪Artificial selection=the
process of selection conducted
under human direction
▪Produced the great variety
of dog breeds and food
crops

18. Evolution generates biodiversity
▪Biological diversity (biodiversity)=the variety of life
across all levels of biological organization
▪Species
▪Genes
▪Populations
▪Communities
▪Scientists have described 1.8 million species
▪Estimates of the total number of species that exist
range from 3 million to 100 million
▪Biodiversity exists nearly everywhere

19. Speciation produces new types of organisms
▪Speciation= the process of generating new
species from a single species
▪Allopatric speciation=species formation due to
physical separation of populations
▪The main mode of speciation
▪Populations can be separated by glaciers, rivers,
mountains
▪Each population gets its own set of mutations
▪Natural selection can speed the process

21. We can infer the history of life’s diversification by
comparing organisms
▪How did the major groups of organisms come to
be?
▪Phylogenetic trees=diagrams that show
relationships among species, groups, genes, etc.
▪Scientists can trace how certain traits evolved
▪Some traits evolved and were passed on
▪Other traits evolved more than once (e.g., the
ability to fly)

23. ▪Knowing how organisms are related to one another
helps scientists organize and name them
▪Categories reflect evolutionary relationships
▪Scientists use physical and genetic characteristics
to organize
▪Each species gets a two-part Latinized scientific
name
We can infer the history of life’s diversification by
comparing organisms

25. The fossil record teaches us about life’s long
history
▪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

26. Speciation and extinction together determine
Earth’s biodiversity
▪Extinction=the disappearance of a species from
Earth
▪Species last 1–10 million years
▪Extinction has historically been a natural occurrence
▪The loss of a species is irreversible
▪Number of species in existence =speciation −
extinction

28. Speciation&
extinction
together
determine
Earth’s
biodiversity
▪Human activity profoundly
affects ratesof extinction
▪Biodiversity loss affects people
directly
▪Food, fiber, medicine,
ecosystem services

30. Some species are especially vulnerable to
extinction
▪Extinction can occur when the environment changes
rapidly and natural selection can not keep up
▪Many factors cause extinction:
▪Severe weather, climate change, changing sea
levels
▪Arrival of new species
▪Being a small population or specialized species

31. Some species are especially vulnerable to
extinction
▪Endemic species=a species that only exists in a certain,
specialized area
▪Very susceptible to extinction
▪Usually have small populations
▪Island species are often endemic and thus at risk
▪Case study:
▪Only one land mammal, a bat, reached Hawai’Inaturally
▪Plants and birds evolved without threats of predators, lost
defense
▪Native species are vulnerable to extinction when enemies
are introduced.

32. Some species are especially vulnerable to
extinction
▪Many U.S. amphibians have very small ranges
▪They are vulnerable to extinction
▪For example, the Yosemite toad, Houston toad,
Florida bog frog
▪Forty salamander species are restricted to areas the
size of a typical county
▪Some U.S. salamander species live on top
of single mountains

33. Earth has
seen several
episodes of
mass
extinctions
▪Background extinction rate=a
constant, slow rate of extinction that
occurs as a part of evolution
▪Mass extinction events=episodes
that killed off massive numbers of
species at once
▪Occurred five times in Earth’s
history
▪50–95% of all species go 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

34. 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
▪Today’s extinction rate is 100–
1000 times higher than the
background rate and rising
▪It will take millions of years for life
to recover

35. II. Ecology
AND THE ORGANISMS

36. We study ecology at several levels
▪Ecology and evolution are tightly intertwined
▪Biosphere=the total of living things on Earth and
the areas they inhabit
▪Community=interacting species that live in the
same area
▪Ecosystem=communities and the nonliving
material and forces they interact with

38. We study ecology at several levels
▪Population ecology=investigates the dynamics of
population change
▪The factors affecting the distribution and abundance
of members of a population
▪Why some populations increases and others
decrease
▪Community ecology=focuses on patterns of species
diversity and interactions
▪Ecosystem ecology=studies living and nonliving
components of systems to reveal patterns
▪Nutrient and energy flows

39. Each organism has habitat needs
▪Habitat=the environment where an organism lives
▪It includes living and nonliving elements
▪Habitat use=each organism thrives in certain habitats,
but not in others
▪Results in nonrandom patterns of use
▪Habitat selection=the process by which organisms
actively select habitats in which to live
▪Availability and quality of habitat are crucial to an
organism’s well-being
▪Human developments conflict with this process

40. Each organism has habitat needs
▪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 during
migration, 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

41. Niche and specialization are key concepts in
ecology
▪Niche=summary of everything an organism does
▪Use of resources
▪Functional role in a community: habitat use, food
selection, role in energy and nutrient flow,
interactions with other individuals

42. Niche and specialization are key concepts in
ecology
▪Specialists=species that have narrow niches
and specific needs
▪Extremely good at what they do
▪But vulnerable when conditions change
▪Generalists=species with broad niches
▪Use a wide array of habitats and resources
▪Can live in many different places

43. III. Population Ecology
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44. Population Ecology
▪Population=individuals of a
particular species that inhabit an
area
▪Species may have different
arrangements of their populations
▪Some populations (like the
nēnē) exist as isolated
populations
▪Others (like humans) exist as
large continuous populations

45. Populations show characteristics that help
predict their dynamics
▪Certain characteristics of a population help
scientists predict what will happen to them in the
future
▪Helps in managing threatened species
▪Population size=number of individuals present at a
given time
▪Populations generally grow when resources are
abundant and predators are few
▪Decline in response to loss of resources, other
species, disasters

47. Population
density
▪Population density=the number
of individuals in a population per
unit area
▪High densities have advantages
and disadvantages
▪Easier to find mates
▪Increased competition and
vulnerability to predation
▪Increased transmission of
diseases
▪Sometimes causes organisms
to leave an area if too dense
▪Low densities provide access to
plentiful resources and space but
make it harder to find mates

48. Population
distribution
▪Population distribution
(dispersion)=spatial arrangement
of organisms
▪Random=haphazardly located
individuals, with no pattern
▪Uniform=individuals are evenly
spaced
▪Territoriality, competition
▪Clumped=organisms found close
to other members of population
▪Most common in nature
▪Clustering around resources
▪Mutual defense

50. Sex ratio and age structure
▪Sex ratio=proportion of males to females
▪In monogamous species, a 1:1 sex ratio maximizes population growth
▪Most species are not monogamous, so ratios vary
▪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 (e.g., a tree)
▪Experience can help older individuals breed more

51. Birth and death rates
▪Survivorship curves=graphs that show that the
likelihood of death varies with age
▪Type I: higher death rate at older ages
▪Larger animals (e.g., humans)
▪Type II: same death rate at all ages
▪Medium-sized animals (e.g., birds)
▪Type III: higher death rate at young ages
▪Small animals, plants

53. Populations may grow, shrink, or remain stable
▪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) per 1000 individuals per year

54. Populations may grow, shrink, or remain stable
▪Natural rate of population increase=
(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 population’s size/1000/year
▪Growth rate as a percent =Population growth
rate ×100%
▪Populations of different sizes can be compared

55. Unregulated populations increase by exponential
growth
▪Exponential growth = whena population increases
by a fixed percent
▪Graphed as a J-shaped curve
▪Exponential growth cannot be sustained indefinitely
▪It occurs in nature with:
▪Small population
▪Low competition
▪Ideal conditions
▪Occurs often with introduced species

57. Limiting factors restrain population growth
▪Limiting factors=physical, chemical, and biological
attributes of the environment that restrain
population growth
▪Space, food, water, mates, shelter, suitable
breeding sites, temperature, disease, predators
▪Carrying capacity=the maximum population size of
a species that its environment can sustain
▪Limiting factors slow and stop exponential growth
▪An S-shaped logisticgrowth curve

59. The influence of some factors depends on
population density
▪Density-dependent factors=limiting factors whose
influence is affected by population density
▪Increased density increases the risk of predation,
disease, and competition
▪Results in the logistic growth curve
▪Larger populations have stronger effects of limiting
factors
▪Density-independent factors=limiting factors whose
influence is not affected by population density
▪Events such as floods, fires, and landslides
▪Few populations in nature match the curve exactly

61. Carrying capacities can change
▪Environments are complex and ever-changing
▪Limiting factors can change, altering the carrying
capacity
▪Humans lower environmental resistance for themselves
▪Increases our carrying capacity
▪Technologies overcome limiting factors
▪In increasing carrying capacity for humans, we now use
immense portions of the planet’s resources
▪We have reduced the carrying capacity for countless
other organisms

62. Reproductive strategies vary among species
▪Biotic potential=an organism’s capacity to produce offspring
▪K-selected species=species with long gestation periods, few
offspring, and strong parental care
▪Have a lowbiotic potential
▪Stabilize at or near carrying capacity; good competitors
▪r-selected species=species that reproduce quickly and offer
little or no care for offspring
▪Have a highbiotic potential
▪Populations fluctuate greatly
▪These are the two extremes—most species fall somewhere in
between

63. IV. Conserving
Biodiversity

64. Conserving Biodiversity
▪Humans are developing land, extracting
resources, and growing as a population
▪This increases the rate of environmental change
for other species
▪Science can help us understand how we are
changing the environment
▪Impacts threatening biodiversity have complex
social, economic, and political roots
▪We must understand these factors to solve
problems

65. Introduced species pose challenges for native
populations and communities
▪Some introduced species thrive in their new
environments, eliminating native species
▪Native island species are particularly vulnerable
▪Evolved in isolation with limited need for
defenses
▪Biologists and land managers often must eradicate
introduced species to protect native habitats
▪In Hawaii, pigs are being hunted and pig-free
areas are being fenced off

66. Innovative solutions are working
▪Scientists, land managers, and private citizens are
protecting the native species and habitats of Hawaii
▪Invasive species are being removed
▪Native species (like the nēnē) are being protected,
and new populations are being started
▪Ranch land is being restored to forest
▪Coral reef communities are part of the largest
federally protected marine reserve in the world
▪This restored and protected land has resulted in
ecotourism=the phenomenon of people visiting the
islands to experience the natural areas

67. Climate change now poses an extra challenge
▪Climate change is altering how we protect species
and habitats
▪Land is typically protected to conserve the species
that live there
▪As the climate changes, the protected land may
no longer support the same species

69. Conclusion
▪The fundamentals of evolution and population
ecology are integral to environmental science
▪Natural selection, speciation, and extinction
help determine Earth’s biodiversity
▪Understanding how ecological processes
function
at the population level is crucial to protecting
biodiversity

70. QUESTION: Review
Which of the following is NOT a part of the
process of natural selection?
a)Once grown, organisms generally do not
have to struggle 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.

71. QUESTION: Review
What happens as a result of adaptation?
a)Species have lower reproductive success
and lower survival.
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 higher survival.

72. QUESTION: Review
Directional selection would result in which of
the following?
a)Dogs with black coats evolving whiter coats
in colder areas
b)Red and white flowers interbreeding,
producing pink flowers
c)Fish evolving bigger eyes as the water gets
muddier
d)A population of birds, some with thicker
beaks that eat seeds and others with
thinner beaks that eat insects

73. QUESTION: Review
Allopatric speciation would occur in
a)one population that mates in May and
another that mates in June.
b)two populations separated by the
Mississippi River.
c)one population that feeds in tree branches
and another that feeds on tree trunks.
d)a population with a mutation that turns fur a
different color than usual.

74. QUESTION: Review
Which of the following statements about
extinction
is true?
a)Extinctions have only started now that
humans are changing the planet.
b)Extinction of one species never benefits
any other organisms in a community.
c)The vast majority of species that have ever
existed are now extinct.
d)Extinction rates stay at a constant
background rate and never change.

75. QUESTION: Review
Which of these species is MOST vulnerable to
extinction?
a)A species whose crude death rate is lower
than its crude birth rate
b)A species distributed in one county of the
United States
c)A species that eats many different plant
species
d)A species that has hundreds of offspring

76. 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.

77. QUESTION: Viewpoints
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 it’s natural.
d)I don’t care; it really does not affect me.

78. QUESTION: Viewpoints
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 can
support.
b)Yes, but technology will keep raising the carrying
capacity, so it’s not much of a problem.
c)No. Humans are no longer constrained by
environmental limits, due to our technology and
ability to manipulate the environment.
d)I don’t care; it really does not affect me.

79. QUESTION: Interpreting Graphs and Data
Which type of distribution is a
result of competition between
individuals?
a)Random
b)Uniform
c)Clumped
d)None of these

80. QUESTION: Interpreting Graphs and Data
What does this graph show?
a)The effects of carrying
capacity on population
growth
b)A population that keeps
growing
c)The effects of
exponential growth
d)The effects of
increasing carrying
capacity