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

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

6. 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

7. 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. 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.

10. 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

11. 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

13. 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

15. 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

17. 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

18. Speciation produces new types of organisms
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

20. 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)

22. We can infer the history of life’s diversification by comparing organisms
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

24. 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

25. 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

27. Speciation and extinction together determine Earth’s biodiversity
Human activity profoundly affects rates of extinction
Biodiversity loss affects people directly
Food, fiber, medicine, ecosystem services

29. 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

30. 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

31. 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. The Geologic Record

36. Macroevolution

37. 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

39. 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 increase 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

40. 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

41. 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

42. 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

43. 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

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 = when a 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 logistic growth 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

60. The logistic growth curve is a simplified model
Few populations in nature match the curve exactly

62. 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

63. 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 low biotic 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 high biotic potential
Populations fluctuate greatly
These are the two extremes—most species fall somewhere in between

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?
Once grown, organisms generally do not have to struggle to survive.
Organisms produce more young than can survive.
Individuals vary in their genetic characteristics.
Some individuals are better suited to their environment than others.
Answer: a 70

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

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

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

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

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

76. QUESTION: Review A community is defined as
the total of living things on Earth.
members of the same population that can interbreed.
interacting species in an area.
species and the nonliving material they interact with.
Answer: c 76

77. QUESTION: Viewpoints Should we care whether a species goes extinct?
Yes, because all life is important and valuable.
Yes, because we are causing this wave of extinction, so we should fix it.
We should not, because it’s natural.
I don’t care; it really does not affect me.
Answer: any 77

78. QUESTION: Viewpoints
Do you think humans are subject to limiting factors and, ultimately, a fixed carrying capacity?
Yes. Although we have raised the carrying capacity, there are limits to the number of humans Earth can support.
Yes, but technology will keep raising the carrying capacity, so it’s not much of a problem.
No. Humans are no longer constrained by environmental limits, due to our technology and ability to manipulate the environment.
I don’t care; it really does not affect me.
Answer: any 78

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

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