Lecture 25

Question 1

3 levels of biodiversity and description

Answer 1

Genetic diversity: amount of genetic variation that occurs within & between populations of a single species. If 1 pop goes extinct, genetic diversity may ↓
Necessary for the survival of the species

Species diversity: diverse # of species. Greater variety of species= ecosystem that can withstand more pressures

Community & ecosystem diversity: changes can lead to disruptions in food chains & nutrient cycling

Question 2

local vs global extinction

Answer 2

Local extinction: a species is lost from a particular ecosystem.

Global extinction: a species is lost from all ecosystems

Question 3

Why should we bother to preserve biodiversity?

Answer 3

Ethical responsibility to protect (or at least not harm) other life forms

To preserve the essential services that ecosystems perform: clean the air & water, decompose dead organisms, pollinate our crops, nutrient cycling, climate regulation…

Humans depend on plants, animals & microorganisms for a wide range of food, medicine, & industrial products

Question 4

How humans decrease biodiversity (4 major threats)

Answer 4

Habitat loss
Overharvesting
Introduced/invasive species
Global change

Question 5

Biggest cause of decrease in biodiversity?

Answer 5

habitat lost

Question 6

Causes of habitat loss:

Answer 6

Clearing land for agriculture
Urban development
Forestry, mining
Pollution of water and land
Climate change

Question 7

Overharvesting?

Answer 7

Harvesting or hunting of wild plants or animals at rates exceeding the ability of populations of those species to rebound.
Problem especially for slowly
reproducing animals &
those restricted to living in a small area

Question 8

Introduced species ?

Answer 8

those that humans move from native locations to new geographic regions (accidental or intentional)

Question 9

bioaccumulation & biomagnification

Answer 9

If an organism can’t break down the toxin, it gets stored (usually in fatty tissue): this is called bioaccumulation

If that organism gets consumed, the toxins are passed to the next trophic level: this is called biomagnification

Bioaccumulation: Build-up of a toxin in an organism

Biomagnification: Build-up of a toxin as it passes from one trophic level to the next

Question 10

Greenhouse effect

Answer 10

Process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, & is re-radiated in all directions

• Caused by atmospheric water, CO2, methane
• Necessary to keep the surface of the Earth at a habitable temperature

Excessive greenhouse effect can lead to global warming and changes in climate

Question 11

Some factors that contribute to famine

Answer 11

Drought, floods, invasive species
Pollution: damaged crops, polluted waters
Deforestation
Over everything: Overgrazing, over-fishing, over-hunting

Question 12

Extinction vortex

Answer 12

inbreeding and genetic drift combine to cause a smaller population to shrink. why? loss of genetic variation