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27 Cards in this Set

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Define Evolution

Genetically based change in the appearance, functioning, and/or behavior of organisms across generations, often by the process of natural selection.

Define Adaptation

The process by which traits that lead to increased reproductive success in a given environment evolve in a population through natural selection.



What is Natural Selection?

The process by which traits that enhance survival and reproduction are passed on more frequently to future generations of organisms than traits that do not, thus altering the genetic makeup of populations through time. Natural selection acts on genetic variation and is a primary driver of evolution.

Components of Natural Selection


(The idea of natural selection is based on a few premises. )

1. Populations of organisms have the potential to reproduce rapidly.


2. Not all offspring in a population will survive.


3. Individuals vary within a population.


4. This variability is genetically inherited


5. Individuals with beneficial genes will survive, reproduce, and pass that characteristic onto their offspring while those that do not possess beneficial traits will die.



What does Natural Selection act on?

The environment in which an organism is found acts as a selective force. This is where the term natural selection comes from.

What is Directional Selection?


Kinds of Natural Selection

Directional selection occurs when there is a shift in characteristics in the population in one direction. EX. snail shells getting thicker.

What is Stabilizing Selection?


Kinds of Natural Selection

Stabilizing selection is when intermediate forms of the trait are favored, and extreme forms are not favored. EX. Intermediate shells favored, human birth weight. (find more info)

What is Disruptive Selection?


Kinds of Natural Selection

Disruptive selection is when extreme characteristics are favored, intermediate forms are not favored. EX: Thick and thin shells favored in snails. (find more info)

What is Speciation?

The process by which a new species is generated.

How does Speciation Happen?

Speciation is when when one population is geographically separated into two (or more) isolated populations. They will experience genetic divergence in this separated state. Mutation and natural selection will act independently on each population and may change the organisms within each separate population. Note: separate populations may diverge so much that they can no long mate with each other.

What is extinction?

The disappearance of an entire species from Earth.

What makes a species vulnerable to extinction?


Shared characteristics

1. small population size and are endemic to a small area.


2. cannot adapt quickly to changes in their environment.


3. specialists (they only eat one particular food, for example. EX: pandas.

What is background extinction?

The average rate of extinction that occurred before the appearance of humans. For example, the fossil record indicates that for both birds and mammals, one species in the world typically became extinct every 500-1,000 years.

What is Mass Extinction?

The extinction of a large proportion of the world's species in a very short time period due to some extreme and rapid change or catastrophic event. Earth has seen 5 mass extinction events in the past half-billion year. There is debate as to whether we are entering a sixth mass extinction – mostly human caused.

What is Species Diversity?


3 levels of biodiversity

1. The number and variety of species in the world or in a particular region.




The only factors that change species diversity are extinction and speciation.




What most people think of when they think of biodiversity.

What is Ecosystem Diversity?


3 levels of biodiversity

2. The variety of habitats within a particular landscape. Areas with greater ecosystem diversity will have greater species diversity and greater genetic diversity.

What is Genetic Diversity?


3 levels of biodiversity

3. The measure of the variability of individuals within a species. Generally, species that have existed for a longer period of time have greater genetic diversity. Greater genetic diversity allows a species or population to respond better to changing conditions.

How is biodiversity measured?

Biodiversity is often expressed in terms of Species Richness. This component is easily measured and is a good gauge for overall biodiversity.




Species Richness is the number of species in a particular region.

Why is biodiversity unevenly distributed?

Key elements that determine biodiversity are 1. plant productivity and 2. climate stability. For example, greater amounts of solar energy, heat, and humidity at tropical latitudes lead to more plant growth, making areas nearer the equator more productive and able to support larger numbers of animals.




The Latitudinal Gradient is one of the most obvious patterns.

The 5 natural extinction episodes?

1. Ordovician: 440 mya, 20% of families affected, marine organisms.


2. Devonian: 370 mya, 20% of families extinct, marine organisms.


3. Permo-Triassic: 250 mya, 50% families/90% species extinct, marine organisms. Cause: Volcanism, likely.


4. End-Triassic: 202 mya, 20% families/50% genera extinct, marine organisms.


5. Cretaceous-Tertiary: 65mya, 5% families/50% species extinct. Cause: asteroid impact, likely.

What is causing the 6th extinction?

Humans are causing the 6th extinction. Records show that with the arrival of humans, a wave of extinction follows. This extinction is ongoing, and it is affecting large animals, specialized organisms, island organisms, and organisms harvested by people.

The major causes of biodiversity loss?

1. Loss of habitat


2. Pollution


3. Over-harvesting


4. Invasive Species


5. Climate Change

What are the benefits of biodiversity?

Biodiversity contributes to all of the following...


1. Provides ecosystem services: purifies air & water, stabilizes earth's climate, pollinates plants, etc.


2. Enhances food security


3. Provide drugs and medicine


4. Economic benefits through tourism and recreation


5. Valuable connection with nature, or biophilia.

What is conservation biology?

A scientific discipline devoted to understanding the factors, forces, and processes that influence loss, protection, and restoration of biological diversity.

At what levels do conservation biologists work?

Researchers address challenges facing biological diversity at all levels, from genes to species to ecosystems.

What is the Endangered Species Act (ESA)?

It is the primary legislation for protecting endangered species in the US. It forbids the government and private citizens from taking actions that destroy endangered species or their habitats. Also forbids trade in products made from endangered species.

Endangered Species Act: Pros and Cons

Efforts are succeeding in getting endangered species off the list; however, some groups fear that the ESA's efforts put more priority on protecting species rather than on the well-bieng of humans; impeded development; weakened land rights.