Ecosystems species diversity environmental interactions
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Ecosystems – Species Diversity & Environmental Interactions. After this unit you should be able to : Explain the process of natural selection and cite evidence for this process Describe the ways in which evolution influences biodiversity

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Ecosystems species diversity environmental interactions
Ecosystems – Species Diversity & Environmental Interactions

After this unit you should be able to:

  • Explain the process of natural selection and cite evidence for this process

  • Describe the ways in which evolution influences biodiversity

  • Discuss reasons for species extinction and mass extinction events

  • List the levels of ecological organization

  • Outline the characteristics of populations that help predict population growth

  • Assess logistic growth, carrying capacity, limiting factors, and other fundamental concepts in population ecology

  • Identify efforts and challenges involved in the conservation of biodiversity


Learning targets
Learning Targets: Interactions

Natural selection

How evolution influences biodiversity

Reasons for species extinction

Ecological organization

Population characteristics

Population ecology

Conserving biodiversity


Organisms and species
Organisms and Species Interactions

  • Organisms, the different forms of life on earth, can be classified into different species based on certain characteristics.

Figure 3-3


Evolution generates biodiversity
Evolution generates biodiversity Interactions

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 = 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 Interactions

Evolution may be seen as random

directed by natural selection

Natural Selection = traits that enhance survival and reproduction

Are passed on more frequently to future generations

those that do not lead to survival, disappear in the gene pool.


Evolution by natural selection
Evolution by natural selection Interactions

  • Micro-evolution: The concept of change over time.

    • change is through populations of species, not individuals.

    • Occurs over many generations, through environmental influence and genetic variation.

    • Micro-evolution can lead to Macro-Evolution (geologically speaking).

  • It is one of the best-supported and mostinformative concepts in all science

    • It is the main standpoint of modern biology and the basis for Biodiversity.

    • Both, Darwin andWallace proposed natural selection as the mechanism of evolution

    • Knowing ecology and learning the history of life helps us to understand and appreciate environmental science

  • Evolutionary processes influence pesticide resistance, agriculture, medicine, health, etc.


Natural selection shapes organisms
Natural selection shapes organisms Interactions

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

Natural selection acts on genetic variation


Genetic variation
Genetic variation Interactions

Adaptation = the process where, over time, characteristics (traits) that lead to better reproductive success

Become more prevalent in the population

Adaptive trait (leads to 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 through mating preferences.


Natural selection acts on genetic variation
Natural selection acts on genetic variation Interactions

Natural selection changes characteristics through:

Directional selection = drives a feature in one direction

Stabilizing selection = favors intermediate traits

Preserving the status quo

Disruptive selection = traits diverge in two or more directions


Environmental conditions affect selection
Environmental conditions affect selection Interactions

  • Environmental conditions determine the pressures natural selection exerts

    • These pressures affect who survives and reproduces

    • Traits evolve that allow success in that environment

  • But traits that promote success at one time or place may not do so at another

  • Natural selection weeds out unfit individuals

    • It also elaborates and diversifies traits that may produce new species


Selective pressures influence adaptation
Selective pressures influence adaptation Interactions

  • Divergent evolution = Related species in different environments

    • Experience different pressures

    • Evolve different traits

  • Convergent evolution= unrelated species may evolve similar traits

    • Because they live in similar environments


Evidence of natural selection is everywhere
Evidence of natural selection is everywhere Interactions

It is evident in every adaptation of every organism

Artificial Selection = the process of selection conducted under human direction

Producing the great variety of dog breeds and food crops


Evolution generates biological diversity
Evolution generates biological diversity Interactions

  • Biological diversity (biodiversity) = the variety of life across all levels of biological organization

    • Species

    • Genes

    • Environmental

  • Scientists have described 1.8 million species

    • Up to 100 million species may exist

    • Tropical rainforests are rich in biodiversity


Speciation
Speciation Interactions

Speciation produces new types of organisms

The process of generating new species from a single species

Geographic Isolation

Where changes and isolations within the environment and habitat cause new species to form.

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


Another type of speciation
Another type of speciation Interactions

Sympatric speciation= species form from populations that become reproductively isolated within the same area

Feed in different areas or eat different foods.

Mate in different seasons or because of mating rituals.

Hybridization between two species

Mutations

Bird dances: rifle bird ; moonwalk.


Speciation results in diverse life forms
Speciation results in diverse life forms Interactions

How do major groups diverge over time?

Phylogenetic trees(cladograms) = show relationships among species, groups, genes, etc.

Scientists can trace how certain traits evolved


The fossil record
The fossil record Interactions

  • 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


Extinction
Extinction Interactions

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


Extinction is a natural process but
Extinction is a natural process, but … Interactions

Humans profoundly affect rates of extinction

Biodiversity loss affects people directly

Food, fiber, medicine, ecosystem services


Some species are more vulnerable to extinction
Some species are more vulnerable to extinction Interactions

Extinction occurs when the environment changes rapidly

Natural selection can not keep up

Many factors cause extinction:

Severe weather, climate change, changing sea levels

New species, small populations

Specialized species

Endemic species = a species only exists in a certain, specialized area

Very susceptible to extinction

These species usually have small populations


Many u s amphibian species are vulnerable
Many U.S. amphibian species are vulnerable Interactions

Some U.S. salamander species live on top of single mountains

  • Many U.S. amphibians have very small ranges

    • They are vulnerable to extinction

    • The Yosemite toad, Houston toad, Florida bog frog

  • 40 salamander species are restricted to areas the size of a typical county


Striking gold in costa rica
Striking gold in Costa Rica Interactions

In 1964, Golden toads were discovered in Monteverde, Costa Rica

The mountainous cloud forest has a perfect climate for amphibians

They became extinct within 25 years

Climate change’s drying effect on the forest

A lethal fungus