Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
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 |
|
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 |
|
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 |
|
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 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 |
|
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 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 |
|
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 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 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 |
|
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 |
|
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 |
|
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 |