Lecture 21-22: The Biosphere Flashcards
What is the biosphere?
Biological component of the earths system
What are the main “roles” of the biosphere?
- connecting other spheres in matter and energy exchanges
- drives cycling of key elements (CHONPS)
What is the bases of darwinian evolution (3)?
reproduction, mutation and natural selection
What is a “self sustaining” organism?
contains all genetic information required for growth and reproduction
What are the minimum criteria of life?
- Acquire nutrients
- Carry out metabolic reactions
- reproduction
- ability to evolve
What does life need to sustain itself?
- Energy (solar or chemical)
- Water
- Carbon and others (CHONPS)
What was the evolutionary impact of oxygen-producing life?
- 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)
What is a biome?
A group of ecosystems sharing a similar type of flora/fauna under similar climatic regime
(ex: rainforest, tundra, desert, savanna…)
How does latitude and elevation determine biome distributions?
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
What is the relationship between net primary production and evapotranspiration?
Strongly positive: areas with more evapotranspiration have increased net primary production
What is the comparison between the net primary productions of tropical and temperate forests?
On a daily basis, the net primary production is relatively similar, but rainforests have much longer growing seasons so they produce more carbon annually
What is biodiversity?
variability among living organisms (at all levels) and the ecological complexes of which they are part
What are the components of biodiversity?
- species diversity/richness
- genetic diversity
- populations
- communities
- ecological processes
- ecosystems
What is a species?
A group of genetically similar organisms that can interbreed and produce fertile offspring
What is species richness?
of species within a habitat
What is genetic diversity?
genetic variation across species –> the basis for evolutionary change
What is population structure?
variation in behaviour, age, size, morphology amongst individuals in an area
What factors affect species richness
- Area (increased area = increased richness)
- latitude (increased richness @ tropics)
- elevation (increased elevation = decreased richness)
Why is species richness increased at the tropics?
- greater land mass
- milder climate
- stable climate
- species-energy hypothesis
- higher accumulation of species over evolutionary time
What is the species-energy hypothesis?
Greater exposure to solar energy = greater productivity = more species can be accommodated in food webs
T or F: species extinctions are common
True! Almost every species that ever existed has gone extinct
T or F: species with large populations are easy to kill off
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
What is the basis for a species to be considered extinct?
Elimination of all reproducing populations
T or F: extinction of widespread species may result from abnormal stresses.
True! Overhunting can cause a widespread populous species to become extinct
What are possible causes of prehistoric mass extinctions?
- 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)
