4.1 What Is Biodiversity and What Is It Important?

Biodiversity Is a Crucial Part of the Earth’s Natural Capital

• Biological Diversity: Variety in the earth’s species

• Functional Diversity: Variety of processes within an ecosystem

• Genetic Diversity: Variety of genes in a population

• Species Diversity: Number and variety of species

• Ecological Diversity: The variety of ecosystems found in an area or on the earth

4.2 Where Do Species Come From?

Biological Evolution by Natural Selection Explains How Life Changes over Time

• Biological evolution: How life changes over time and it can be seen through the differences in genetic characteristics.

• Natural selection: Individuals with certain traits are more likely to survive and reproduce under a certain set of environmental conditions.

The Fossil Record Tells Much of the Story of Evolution

• Fossils→ Physical evidence of old organisms

• Fossil Record→ Entire body of fossil evidence

• Fossil records can show evolution. They can help also identify features of previous animals, as well as causes of their extinction.

The Genetic Makeup of a Population Can Change

• Mutations: Random changes in DNA molecules

• Natural selection: Acts on individual

• Genetic Resistance: Ability of one or more members of a population to resist a chemical designed to kill it.

Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring

• Adaptation: An organism becomes better suited to its habitat (where it lives) from a genetic trait.

• Differential Reproduction: A phenomenon in which people who possess adaptable genetic qualities have more viable offspring than people who have not.

4.3 How Do Speciation, Extinction, and Human Activities Affect Biodiversity?

• Processes such as the shifting of tectonic plates, volcanic eruptions, and earthquakes influence the earth’s climate and in turn, affect evolution by removing and/or isolating habitats and species.

• Long-term climate changes relocate ecosystems, thus determining where certain species can live.

• Asteroids and meteorites have caused environmental stress and mass extinctions.

How Do New Species Evolve?

• Speciation: One species splits into two or more species

  • This happens when a species is separated whether it is geographically or through gene pool reductions

  • Geographic Isolation: Physical isolation of populations for a long period

  • Reproductive Isolation: This leads to an inability to produce proper offspring when two individuals from separate species mate.

Extinction Is Forever

• Extinction: Process in which an entire species ceases to exist

  • Usually due to disease, low birth rate, and overly specialized species.

  • Human activities also affect rates of extinction

    • Ex; pollution, hunting, artificial selection, introduction of new species (can be invasive to others/threatening)

• Endemic Species: Found only in one area, particularly vulnerable to extinction

• Background Extinction: Typical low rate of extinction

• Mass Extinction: Significant rise above background level

4.4 What Is Species Diversity and Why Is It Important?

• Natural selection can lead to the development of an entirely new species. In speciation, two species arise from one when some members of a population cannot breed with other members to produce fertile offspring. Speciation occurs in two phases:

  • Geographic isolation, physical separation for long time periods.

  • Reproductive isolation.

• When population members cannot adapt to changing environmental conditions, the species becomes extinct.

• When local environmental conditions change, some species will disappear at a low rate; this is called background extinction.

• Mass extinction is a significant rise in extinction rates above the background extinction level. Usually, 25–70% of species are lost. Recent evidence suggests that there have been two mass extinctions on earth. There appear to have been three mass extinctions on earth.

Species Diversity Includes the Variety and Abundundance of Species in a Particular Place

• Species Diversity: The number of different species present in an ecosystem and the relative abundance of each of those species

• Species Richness: The number of different species in a given area

• Species Evenness: Comparative number of individuals of each species present

4.5 What Roles Do Species Play in Ecosystems?

• Species diversity is the number of species (richness) combined with their relative abundance (evenness)

• Species-rich communities tend to be more stable and more productive.

Each Species Plays a Unique Role in Its Ecosystem

• Ecological Niche: Everything that affects survival and reproduction

• Generalist Species: Wide range of tolerance, broad species

• Specialist Species: Narrow range of tolerance, narrow niche

• Indicator Species: Provides us with early warnings of environmental damage.

Niches Can Be Occupied by Native and Nonnative Species:

• Native Species

  • Normally live in an ecosystem

• Nonnative Species

  • Not native

Why Are Species Vanishing?

• Habitat loss

• Prolonged Drought

• Pollution

• Increase in UV Radiation

• Parasites

• Diseases

• Climate Change

• Overhunting

Keystone and Foundation Species Help Determine the Structure and Functions of Their Ecosystems

• Keystone Species: Have a large effect on the types and abundances of other species

• Foundation Species: Species that create habitats and cause a positive effect on diversity

4-6 What roles do species play in ecosystems?

• The ecological niche is a species’ way of life in an ecosystem, everything that affects its survival and reproduction.

  • The niche includes the members’ adaptations; its range of tolerance for physical and chemical conditions, its interactions with other components of the ecosystem, and its role in energy flow and matter recycling.

  • The fundamental niche is the full potential range of conditions and resources a species could potentially use. Its realized niche is part of the potential niche that allows a species to survive and avoid competition with other species for the same resources.

    • Some species have broad ecological roles and are termed generalist species.

    • Some species have narrow ecological roles and are termed specialist species.

• Niches can be occupied by native or non-native species.

• Indicator species provide early warning of ecosystem damage because they have a narrow range of tolerance.

• Keystone species have a large effect on maintaining balance within an ecosystem.

  • Can be, but are not necessarily, pollinators and top predators.

  • Foundation species create and enhance habitats that benefit other species.