BIOA02H3 Chapter Notes - Chapter 50: Sexual Selection, Advantageous, Protein Folding

110 views29 pages
20 Nov 2010
Chapter 52: Ecology and the Distribution of Life
52.1 What is Ecology?
x Ecology is the scientific study of the rich and varied interactions between organisms and their
x Communities are systems embracing all the organisms living together in the same area
x Ecosystems are systems embracing all the organisms living together and the physical
environment they live in
x Biosphere - system that embraces all regions of the planet where organisms live
x Environment - encompasses all biotic and abiotic factors
x Organisms are both influenced and influence the environment
52.2 How are Climates Distributed on Earth?
x Climate - average of the atmospheric conditions found in a region over the long term
x Climate is what you expect, weather is what you get
x Factors that most strongly affect climates: atmospheric and oceanic circulation patterns
x Due to the angle of solar energy arriving at a location, it can cause seasonal variations in
temperature, and circulation patterns. (Roughly 0.4 degrees decrease per 110 km away from
equator at sea level)
x Air temperature also decreases with elevation (rise = expansion = losing moisture)
x Global air circulation patterns result from the global variation in solar energy input and the spin
of the Earth
x At equator (Tropics), warm air rises, replaced by cool air from 30o North and South.
x The coming together of these air masses produces the intertropical convergence zone - where
the rising air cools and releases its moisture
x The air that moved into the ICZ, is in turn replaced by the air that has risen and cooled
x This air warms and heats up and picks up moisture (results in deserts)
x At 60o N and S, air rises again and descends at the poles
o Rotational speed of Earth at the equator is quite high - air speeds are relatively slower
o Rotational speed of Earth at pole is non-existent, air speeds are quite high
o Therefore, in the Northern Hemisphere, latitudally moving air masses are deflected to
the right; and those in the Southern are deflected left
o Air masses moving toward the equator become trade winds (veer to become northeast
(coming from north) and south east (coming from south))
o Air masses moving away become Westerly winds
x As air masses pass over a mountain, the windward side gets precipitation; the leeward side gets
a rain shadow
x The air pattern circulation also drives ocean currents
x The tradewinds cause a westerly current until a continent is reached (Transfer of heat to high
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 29 pages and 3 million more documents.

Already have an account? Log in
x The deflection at the continent causes the water to go N or S, where it veers right/left, until
another continent is reached - causing a cycle.
x Dispersal - movement of an individual to seek new places when local conditions seem
x Migration - one response to cyclical environmental changes
52.3 What is a Biome?
x A biome is a terrestrial environment defined by the growth forms of its plants
x The distributions of plants are strongly influcned by annual patterns of termpature and rainfall
x Species richness - the number of species present in its communities
1. Tundra
x Found in arctic and at high elevations in mountains
x Dominated by low-growing perennial plants
x Permafrost - soil with water permanently frozen
2. Boreal forest
x Found toward equator from Arctic tundra, and at lower elevations in mountains
x Long winters, short warm summers
x Evergreen trees dominate
x Temperate Evergreen forests grow along the western coasts of continents at middle to
high latitudes in both hemispheres - winters are very wet and summers are cool and dry
3. Temperate Deciduous Forest
x Temperatures fluctuate dramatically though precipitation is relatively evenly distributed
x Species rich - insects and amphibians
4. Temperate Grasslands
x Dry for much of the year
x Precipitation is variant; most plant life converted to agriculture
x Mammal rich; plants are adapted to grazing and fire
5. Cold Desert
x Found in interiors of large continents in the rain shadows of mountain ranges
x Temperature variance is great
x Dominated by few shrubs and seed eating animals
6. Hot Desert
x More diverse vegetation than cold deserts (Succulent plants)
x Rich fauna of rodents, insects, lizards, and snakes
7. Chaparral
x Form where cool ocean currents flow offshore
x Winters are cool and wet; summers opposite
x Lots of rodents supported by abundant annuals
8. Thorn Forest and Tropical Savanna
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 29 pages and 3 million more documents.

Already have an account? Log in
x Share same climate
x Thorn forests are found on the equatorial sides of hot deserts
o Small shrubs and trees that drop their leaves during long, dry winters (Acacia)
x Tropical savanna have expanses of grasses and grasslike plants with scattered trees
o If not grazed, browsed, or burnt, it typically reverts to a dense thorn forest
9. Tropical Deciduous Forest
x Hot lowlands
x Most trees are deciduous
x Rich soil
10. Tropical Evergreen Forest
x Highest species rich of all biomes
x Most nutrients are tied up with vegetation - soil is poor
52.4 What is a Biogeographic Region?
x Biogeography - the scientific study of the patterns of distribution of populations, species, and
ecological communities
x Biogeographic regions are based on the taxonomic composition of the organisms living in them
x The biotas of biogeographic regions differ because oceans, mountains, deserts, and other
barriers restrict the dispersal of organisms between them.
x A species found only within a certain region is said to be endemic to the region
x Three advances changed the field of biogeography:
1. Continental Drift
x Alfred Wegener proposed this in 1912 (continents moved due to plate tectonics)
x 280 million years ago, one land mass was present Pangaea
x As continents split, evolution occured at different levels
x However, some ancestry was present on Pangaea itself, thus accounting for similar
species in various biogeographic regions
2. Phylogenetic Taxonomy
x Biogeographers transformed phylogenetic taxonomy trees into Area phylogenies by
replacing the names of the taxa with where they were found
x This allowed the tracking of dispersal and speciation
3. Island biogeography
x Developed by Robert MacArthur and Edward O. Wilson to help explain why oceanic
islands always have fewer species than a mainland area of equivalent size
x Immigration of new species v. Extinction of species (assumption: no speciation
occured when accounting for data)
x As species arrive from the species pool into the island, the arrival rate decreases
when ultimately the difference between species pool and island = 0.
x Extinction rates increase as new species enter the island due to biotic and abiotic
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 29 pages and 3 million more documents.

Already have an account? Log in

Get access

$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
Booster Classes
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
Booster Classes