5_Threats to Biodiversity & Extinction

Incomplete set

How many extinction episodes have occurred so far on earth?

5, currently going through the 6th

What is the number of species present on an island determined by?

A balance between immigration and extinction

• Generally, as the number of species present increases, the immigration rate decreases and the extinction rate increases

What are two important, general relationships in the Equilibrium Hypothesis of Island Biogeography?

1. Immigration higher on near islands than distant islands (in relation to mainland), so the equilibrium number of species present will be greater on near islands

2. Extinction higher on small islands than on larger islands, so the equilibrium number of species present will be greater on large islands

Determine the Graph:

• Small, far islands with a low species number have a low immigration rate as well as low extinction rates. If they were to increase in species, extinction rate would increase.

• Large, near islands with a large number of species have low extinction rates. As immigration increases, extinction rate will increase.

What is The Island Biogeography Model? What does it do?

explains the species-area relationship: as area increases, the number of species present (diversity) also increases

S = CA^z

S = number of species

A = area

Island Biogeography Model (S=CA^z):

What factors influence z?

• climate (e.g., latitudinal gradient factors)

• habitat complexity

• isolation (e.g., distance from the mainland)

• types of species represented (e.g., mammals vs birds)

What are the major threats to biodiversity?

• Habitat loss / degradation

• Overexploitation

• Invasive species and disease

• Pollution

• Climate change

What are some examples of species and habitats affected by these threats?

What are the major threats to biodiveristy? The top three?

1. Habitat loss / degradation

2. Overexploitation

3. Invasive species and disease

Give an example of this threats impact on biodiversity:

Overexploitation

Give an example of this threats impact on biodiversity:

Pollution

Give an example of this threats impact on biodiversity:

Invasive Species

Give an example of this threats impact on biodiversity:

Diseases

Give an example of this threats impact on biodiversity:

Climate Change

What are the negative consequences to biodiversity of habitat fragmentation?

What are edge effects? How are species and habitats affected by edge effects?

Edge Effects — altered environmental and biological conditions at the edges of a fragmented habitat

1. Microclimate changes

2. Increased incidence of fire

3. Interspecies interaction (exotic & pest species; domestic species)

4. Potential for disease

Population Effects

1. Limits to dispersal and colonization

2. Restricted access to food and mates

3. Creation of smaller populations

How do habitat fragments differ from the original habitat?

1. Fragments have a greater amount of edge per area of habitat

2. The center of each habitat fragment is closer to an edge

3. Large populations are divided into smaller populations

What are three pollution problems that threaten biodiversity?

1. Pesticide pollution

   • Biomagnification

2. Water pollution

   • Pesticides, herbicides, etc.

   • Eutrophication (nitrates and phosphates)

   • Microplastics

3. Air pollution

   • Acid rain, ozone production and nitrogen deposition, toxic metals

Define: Endemic Species

species found in one place and no where else

Define: Exotic Species

species transported or established outside its native range by the activities of humans, whether done so intentionally or not

Define: Invasive Species

species that become established and proliferate in new (i.e.. nonhistorical) ranges where they cause environmental harm