Lecture 21-22: The Biosphere

Question 1

What is the biosphere?

Answer 1

Biological component of the earths system

Question 2

What are the main “roles” of the biosphere?

Answer 2

• connecting other spheres in matter and energy exchanges
• drives cycling of key elements (CHONPS)

Question 3

What is the bases of darwinian evolution (3)?

Answer 3

reproduction, mutation and natural selection

Question 4

What is a “self sustaining” organism?

Answer 4

contains all genetic information required for growth and reproduction

Question 5

What are the minimum criteria of life?

Answer 5

1. Acquire nutrients
2. Carry out metabolic reactions
3. reproduction
4. ability to evolve

Question 6

What does life need to sustain itself?

Answer 6

1. Energy (solar or chemical)
2. Water
3. Carbon and others (CHONPS)

Question 7

What was the evolutionary impact of oxygen-producing life?

Answer 7

• Atmospheric O2 increases and CO2 decreases
• Ozone layer development
• reduced dominance of anaerobic bacteria
• promoted evolution of more efficient energy uses (mitochondria)
• allowed larger animals to develop (since there is now enough o2 to sustain them)

Question 8

What is a biome?

Answer 8

A group of ecosystems sharing a similar type of flora/fauna under similar climatic regime
(ex: rainforest, tundra, desert, savanna…)

Question 9

How does latitude and elevation determine biome distributions?

Answer 9

Elevation: sea level has more rain, higher up you go, it becomes dryer (ex: polar to tundra to temperate forest to tropical rainforest)

Latitude: same thing as elevation as you get further from the equator

Question 10

What is the relationship between net primary production and evapotranspiration?

Answer 10

Strongly positive: areas with more evapotranspiration have increased net primary production

Question 11

What is the comparison between the net primary productions of tropical and temperate forests?

Answer 11

On a daily basis, the net primary production is relatively similar, but rainforests have much longer growing seasons so they produce more carbon annually

Question 12

What is biodiversity?

Answer 12

variability among living organisms (at all levels) and the ecological complexes of which they are part

Question 13

What are the components of biodiversity?

Answer 13

• species diversity/richness
• genetic diversity
• populations
• communities
• ecological processes
• ecosystems

Question 14

What is a species?

Answer 14

A group of genetically similar organisms that can interbreed and produce fertile offspring

Question 15

What is species richness?

Answer 15

of species within a habitat

Question 16

What is genetic diversity?

Answer 16

genetic variation across species –> the basis for evolutionary change

Question 17

What is population structure?

Answer 17

variation in behaviour, age, size, morphology amongst individuals in an area

Question 18

What factors affect species richness

Answer 18

1. Area (increased area = increased richness)
2. latitude (increased richness @ tropics)
3. elevation (increased elevation = decreased richness)

Question 19

Why is species richness increased at the tropics?

Answer 19

• greater land mass
• milder climate
• stable climate
• species-energy hypothesis
• higher accumulation of species over evolutionary time

Question 20

What is the species-energy hypothesis?

Answer 20

Greater exposure to solar energy = greater productivity = more species can be accommodated in food webs

Question 21

T or F: species extinctions are common

Answer 21

True! Almost every species that ever existed has gone extinct

Question 22

T or F: species with large populations are easy to kill off

Answer 22

False! small populations have higher risks:
- demographic bad luck (minor glitches could wipe them all out)
- small gene pool (can’t adapt to environmental changes)
- thinly spread populations = more difficult to mate

Question 23

What is the basis for a species to be considered extinct?

Answer 23

Elimination of all reproducing populations

Question 24

T or F: extinction of widespread species may result from abnormal stresses.

Answer 24

True! Overhunting can cause a widespread populous species to become extinct

Question 25

What are possible causes of prehistoric mass extinctions?

Answer 25

• volcanic eruption (soot in air causes global cooling or lava floods cause global warming)
• fall in sea level (reduces marine habitat and oxidation of exposed org material removes O2 and releases CO2)
• global climate change (cooling, drying, etc)