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39 Cards in this Set

  • Front
  • Back
Central Case Study: Striking Gold in a Costa Rican Cloud Forest
Golden toads were discovered in Monteverde, Costa Rica in 1964.
200 males in a 16-ft. area
The mountainous cloud forest was ideal for amphibians
The toads vanished from Earth within 25 years
Climate change caused the forest to dry out
A fungus also killed them
Species
a population or group of populations …
Whose members share characteristics and ….
Can breed with each other to produce fertile offspring
Population
a group of individuals of a species that live in the same area
Evolution
means change over time
Biological evolution: genetic change in populations over time
Genetic changes lead to changes in appearance, functioning, or behavior over generations
Natural selection
Natural selection: The process whereby inherited characteristics that enhance survival and reproduction …
Are passed on more frequently to future generations than those that do not

'Evolution may be random 
Or directed by natural selection
Natural selection: The process whereby inherited characteristics that enhance survival and reproduction …
Are passed on more frequently to future generations than those that do not

'Evolution may be random
Or directed by natural selection
Evolution by natural selection
It is one of the best-supported and most illuminating concepts in science
It is the foundation of modern biology
It is vital for a full appreciation of environmental science
Knowing ecology and learning the history of life
Evolutionary processes influence agriculture, pesticide resistance, medicine, health, etc.
In 1858, both Darwin and Wallace proposed natural selection as the mechanism of evolution
Natural selection shapes organisms
Natural selection explains nature’s patterns
Premises of natural selection:
Organisms struggle to survive and reproduce
They produce more offspring than can survive
Individuals of a species vary in their characteristics because of genes and the environment
Some individuals are better suited to their environment and reproduce more effectively
Natural selection acts on genetic variation
Species adapt to the environment - Adaptive trait (adaptation)
A parent that produces more offspring passes on more genes to future generations
Over time, characteristics (traits) that lead to better reproductive success become more prevalent
Adaptive trait (adaptation): a trait that promotes reproductive success
Sexual reproduction also leads to genetic variation
Producing new combinations of genes
Environmental conditions determine the pressures of natural selection
Organisms need time to adapt to changing conditions
Natural selection leads to biodiversity
Natural selection weeds out unfit individuals

It also helps elaborate and diversify traits 
Which leads to the formation of new species
Natural selection weeds out unfit individuals

It also helps elaborate and diversify traits
Which leads to the formation of new species
Evidence of natural selection is everywhere - Artificial selection
Evidence of natural selection is everywhere - Artificial selection
It is evident in every adaptation of every organism
Artificial selection: the process of selection conducted under human direction
Producing the great diversity of dog breeds and crops
It is evident in every adaptation of every organism
Artificial selection: the process of selection conducted under human direction
Producing the great diversity of dog breeds and crops
Evolution generates biological diversity - Biological diversity (biodiversity)
the variety of life across 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 - Allopatric speciation
The process of generating new species from a single species
Allopatric speciation: species form as a result of physical separation of populations
The main mode of speciation
Populations can be separated by glaciers, rivers, mountains
Each popu...
The process of generating new species from a single species
Allopatric speciation: species form as a result of physical separation of populations
The main mode of speciation
Populations can be separated by glaciers, rivers, mountains
Each population, with its own set of mutations, diverges
Speciation results in diverse life forms - Phylogenetic trees
branching diagrams show relationships among species, groups, genes, etc.
Represent life’s history
branching diagrams show relationships among species, groups, genes, etc.
Represent life’s history
Fossils also show life’s history
Fossil: an imprint in stone of a dead organism

Fossil record: the cumulative body of fossils worldwide

Phylogenetic trees and the fossil record show:
Life has existed on Earth for 3.5 billion years
Life evolved complex structures from simple ones
Life evolved large sizes from small ones
But natural selection can also favor simplicity and small size
Extinction
Most species that once lived are now gone
Extinction: the disappearance of a species from Earth
Species last 1–10 million years
Biological diversity is now being lost at an astounding rate
This loss of species is irreversible

Number of sp...
Most species that once lived are now gone
Extinction: the disappearance of a species from Earth
Species last 1–10 million years
Biological diversity is now being lost at an astounding rate
This loss of species is irreversible

Number of species = speciation – extinction
Some species are vulnerable to extinction - Endemic species
Extinction occurs when the environment changes rapidly
Natural selection can’t keep up, so species can’t adapt
Many factors cause extinction:
Climate change, changing sea levels, severe weather
Arrival of new species, small populations
Specialized species
Endemic species: exists only in a certain, specialized area
Very susceptible to extinction
These species usually have small populations
Earth has had several mass extinctions -
Background extinction rate: extinction usually occurs slowly, one species at a time

Mass extinction events: killed off massive numbers of species at once

Occurred five times in Earth’s history
50–95% of all species went extinct at one time
Cretaceous-Tertiary (K-T) event: 65 million years ago
A gigantic asteroid caused dinosaur extinction
End-Permian event: 250 million years ago
75–95% of species went extinct from unknown causes
The sixth mass extinction is upon us
Humans are causing the sixth mass extinction event
Population growth, development, resource depletion
Destruction of natural habitats
Hunting and harvesting of species
Introduction of non-native species
This loss affects humans
We need organisms for food, fiber, medicine, services
Amphibians are disappearing faster than any other group
170 species have already vanished
Ecology:
studies interactions among organisms
And their environment
Ecology and evolution are tightly intertwined
studies interactions among organisms
And their environment
Ecology and evolution are tightly intertwined
Biosphere & Ecologist
the total living things on Earth
And the areas they inhabit

Ecologists: study relationships at higher levels
Levels of ecological studies
Organismal ecology examines relationships between individuals and their environment

Population ecology: investigates population changes
The distribution and abundance of individuals
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
Each organism has habitat needs
Habitat: the environment where an organism lives
It includes living and nonliving elements
Habitat use: nonrandom patterns where organisms live
Habitat selection: the process by which organisms actively select habitats in which to live
Species use different criteria to select habitat
Soil, topography, vegetation, other species
Species have different habitat needs
Depending on body size, season, etc.
Species survival depends on having suitable habitats
The niche: a multidimensional concept
Niche: an organism’s use of resources
Along with its functional role in a community
Habitat use, food selection, role in energy and matter 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
Survive in many different places
Population size
Population size: the number of individuals present at a given time
Can increase, decrease, cycle, or remain the same

Humans drove passenger pigeons, North America’s most abundant bird, to extinction
Population size: the number of individuals present at a given time
Can increase, decrease, cycle, or remain the same

Humans drove passenger pigeons, North America’s most abundant bird, to extinction
Population density
Population density: the number of individuals in a population 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
Also increase transmission of diseases
Low densities make it harder to find mates
But individuals enjoy more space and resources
Population distribution (dispersion)
Population distribution (dispersion): spatial arrangement of organisms

Random: haphazardly located individuals, with no pattern - Resources are widespread

Uniform: evenly spaced individuals

Territoriality, competition

Clumped: most com...
Population distribution (dispersion): spatial arrangement of organisms

Random: haphazardly located individuals, with no pattern - Resources are widespread

Uniform: evenly spaced individuals

Territoriality, competition

Clumped: most common in nature
Arranged according to resources
Sex ratios and age structure
Sex ratio: proportion of males to females
In monogamous species, a 1:1 sex ratio maximizes population growth

Age structure (distribution): the relative numbers of organisms of each age in a population
Helps predict population growth or decline
In species that continue growing as they age
Older individuals reproduce more (e.g., a tree)
Experience makes older individuals better bre
Four factors of population growth or decline
Natality: births within the population

Mortality: deaths within the population

Immigration: arrival of individuals from outside the population
Births and immigration add individuals to a population

Emigration: departure of individuals from the population
Deaths and emigration remove individuals
Population growth rate
Growth rate: rate of change in a population’s size per unit time
Equals (birth rate + immigration rate) – (death rate + emigration rate)
Tells us the net changes in a population’s size per 1000 individuals per year
Growth rate is expressed as a percent:
Population growth rate * 100%
Populations of different sizes can be compared
Exponential population growth
Exponential growth: a population increases by a fixed percent

Graphed as a J-shaped curve
It occurs in nature with:
Small populations
Low competition
Ideal conditions
Exponential growth: a population increases by a fixed percent

Graphed as a J-shaped curve
It occurs in nature with:
Small populations
Low competition
Ideal conditions
Limiting factors restrain population growth
Exponential growth rarely lasts

Limiting factors: physical, chemical, and biological attributes of the environment limiting population growth

Environmental resistance: all limiting factors together
Stabilizes the population size at its carrying capacity
Terrestrial animals: space, food, water, mates, shelter, breeding sites, temperature, disease, predators
Plants: sunlight, moisture, soil chemistry
Aquatic systems: salinity, sunlight, temperature, etc.
Carrying capacity
Carrying capacity: the maximum population size the environment can sustain

Determined by limiting factors
Limiting factors slow and stop exponential growth
Forms an S-shaped logistic growth curve
Carrying capacity: the maximum population size the environment can sustain

Determined by limiting factors
Limiting factors slow and stop exponential growth
Forms an S-shaped logistic growth curve
Population density affects limiting factors
Density-dependent factors: limiting factors whose influence is affected by population density
Increased density increases the risk of predation, competition for mates, and disease
Results in the logistic growth curve
Environmental resistance has a stronger effect on larger populations

Density-independent factors: limiting factors whose influence is not affected by population density
Temperature extremes, floods, fires, and landslides
Carrying capacities can change
Environments are complex and ever-changing
The carrying capacity can change
Humans lower environmental resistance for ourselves
Increasing our carrying capacity
Technologies have overcome limiting factors
We have appropriated immense amounts of resources
But by increasing the carrying capacity for humans
We have reduced the carrying capacity for countless other organisms
Calling into question our own long-term survival
Reproductive strategies vary among species
K-selected species & r-selected species & Biotic potential
Biotic potential: an organism’s capacity to produce offspring

K-selected species: species with long gestation periods and few offspring (i.e., a low biotic potential)
Offspring have a high likelihood of survival
The population stabilizes at or near carrying capacity
Good competitors

r-selected species: species that reproduce quickly
Have a high biotic potential
Little parental care, populations fluctuate greatly
Population changes affect communities
Scientists have noticed troubling changes in the environment
As Monteverde dried out, species have disappeared
Golden toads, harlequin frogs, and more had been pushed from their cloud-forest habitat into extinction
Species from lower, drier habitats moved into the cloud forest
Population sizes of cloud-forest bird species declined
Changing climate and disease are causing population fluctuations and changing the makeup of communities
Conserving biodiversity
Human development, resource use, and population pressure are changing populations and communities
Factors threatening biodiversity have complex social, economic, and political roots
We must understand these factors to solve problems
Millions of people are working to protect biodiversity and to safeguard ecological and evolutionary processes
Costa Rica’s protection is paying off
Costa Rica was losing forests at the world’s fastest rate
Now, 25% of its area is under protection
Ecotourism: tourists visit protected areas

Ecotourism provides thousands of jobs and billions of dollars to Costa Rica’s economy
Costa Rica was losing forests at the world’s fastest rate
Now, 25% of its area is under protection
Ecotourism: tourists visit protected areas

Ecotourism provides thousands of jobs and billions of dollars to Costa Rica’s economy
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