Life Environments

Lecture 7

Copyright © 2012 Joe Marx.

Life Environments Image courtesy of NOAA. Page 2

Topics for This Lecture• What is ecology?• What causes wind, weather and climate?• What terrestrial, marine and freshwater

environments are available to organisms?

Coral reef ecosystem, Rapture Reef, French Frigate Shoals, northwestern Hawaiian Islands.

Life Environments Image courtesy of NOAA. Page 3

• The study of the factors that govern the distribution and abundance of organisms within natural environments.– Each species has its own ecological niche or way of

relating to its environment.• A niche includes the species’ required physical and

chemical situation, nutrient needs, and modes of interaction with surrounding species.

Ecology

◄ Do whales and birds live in similar ecological niches?

Life Environments Image courtesy of USAID. Page 4

• How a species lives within its niche—how it obtains food, reproduces, and emplaces itself or moves about.– Physical, chemical and biological conditions are

limiting factors on life habits and restrict the distribution and abundance of species.

Life Habit

The trees in this Bangladeshi forest compete with each other for light. ►

• Competition among plant species for light, mineral nutrition and soil water are examples of limiting factors.

Life Environments Image courtesy of U.S. Department of Transportation. Page 5

Ecological Groupings• A population is a group of individuals belonging to

one species and living within a particular area.– When populations of several species live together,

they form an ecological community.• An ecosystem consists of all the organisms within an

ecological community, plus the physical environment they live in.

◄ Forest ecosystem in Georgia.

Life Environments Image in the public domain. Page 6

Food Chain• The simplest representation of

energy flow within an ecosystem.– At the bottom of the chain is the

energy stored in plants, which are eaten by small organisms, which are eaten by progressively larger organisms, up to a top predator.

Example of a food chain in a Swedish lake. Osprey feed on northern pike, which feed on perch which eat bleak that

feed on freshwater shrimp. Although not shown, the primary producers of this food chain are probably phytoplankton. ►

Life Environments Image courtesy of U.S. Geological Survey. Page 7

Food Web• A complex network of feeding relationships

within an ecosystem.– More realistic than a food chain as a depiction of

energy flow within an ecosystem.

A marine food web in Alaska. ►

Life Environments Page 8

Flow of Material• The continuous cycling of matter through

ecosystems, which carries energy to the organisms within them.

Plants

NutrientsTransforming

Bacteria

Decomposing Bacteria

Scavengers

Parasites

Herbivores

Carnivores

Sunlight

Life Environments Image courtesy of Horst Frank. Page 9

Atmosphere• The gaseous envelope that surrounds Earth.

– Composed mostly of N2 (78.1%), O2 (20.9%), Ar (0.9%) and CO2 (0.04%).

– Unevenly heated by the Sun.

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Simple Circulation• In the atmosphere, as in any fluid, uneven

warming causes convection, a movement of molecules that distributes the heat more evenly.– If Earth did not rotate, the air warmed at the

Equator would move directly toward the Poles.• Each hemisphere would have a circular flow (gyre):

1. Air heated at the Equator would thin and rise.

2. The rising air would radiate heat and gradually cool.

3. The cooled air would move north or south to escape the warmer air rising beneath it.

4. The air would move aloft to the nearest pole, where it would have to descend.

5. The air would return near the surface, steadily regaining heat.

Image modified from The Atmosphere,Lutgens and Tarbuck, 8th edition, 2001.

• The tendency of moving air to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.– C

• Each time a molecule ofair moves some distance poleward, Earth’s rotation also carries it sidewards.

Life Environments Video and image courtesy of NASA. Page 11

Coriolis Effect

– Caused by Earth’s rotation, which is rightward when viewed north from the Equator and leftward when viewed south from the Equator.

Life Environments Image courtesy of NASA. Page 12

Atmospheric Circulation• The Coriolis Effect causes Earth’s atmosphere to

circulate in six gyres, instead of two.

Intertropical Convergence Zone• The area encircling Earth near the Equator where

surface winds originating in the Northern and Southern Hemispheres come together.

EnvironmentsLeft-hand image courtesy of Mats Halldin.

Right-hand image courtesy of NASA. Page 13

The band of storms marks the Intertropical Convergence Zone

on 19 August 2009. Hurricane Bill is in the central Atlantic.

Because the continents are concentrated in the Northern Hemisphere, the Intertropical

Convergence Zone moves farther from the Equator during the Northern summer than the

Southern summer.

Life EnvironmentsLeft-hand image courtesy of National Park Service.

Right-hand image courtesy of Achim Raschka. Page 14

Biogeography• The study of the distribution and abundance of

organisms, often on a broad geographic scale.

Range of the Western Rattlesnake.

Distribution of the Onychophorans Peripatidae (green) and Peripatopsidae (blue)

Image courtesy of Wikimedia Commons.Life Environments Page 15

Geographical Distribution• Physical barriers and environmental temperature

are the most important limiting factors that affect the distribution of species.– Vegetative patterns on land closely parallel climatic

zones, which are largely controlled by latitude.– Because plants are highly sensitive to climate,

plant fossils are useful indicators of past climates.

Cycads in the Orto Botanico,Palermo, Italy. ►

Life Environments Image copyright © Karen A. Lemke, klemke@uwsp.edu. Page 16

Major Terrestrial Biomes• A biome is the entire community of organisms

living within a single major ecological area.

North American biomes. ►

Life Environments

Upper images courtesy of National Oceanographic and Atmospheric Administration.

Lower-right image courtesy of Wikipedia. Page 17

Cold-Climate Biomes

▲ Tundra on Wrangel Island, Russia.

▲ Northern boreal forest, Copper River, Alaska.

Mountain vegetation, Mojanda, Ecuador. ►

Left and upper-right images courtesy of Wikipedia. Lower-right image courtesy of Wikimedia Commons.

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Temperate-Climate Biomes

▲ Temperate grassland, the Palouse, eastern Washington.

Mediterranean vegetation, Sonoma Mountain, California. ►

Temperate forest, Diqing, Yunnan, China. ►

Left-hand images courtesy of Wikimedia Commons. Right-hand image courtesy of Wikipedia.

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Tropical-Climate Biomes

▲ Daintree Rainforest, Queensland, Australia.

◄ Tropical seasonal forest, Bandipur, India.

◄ Tropical savannah, Gran Chaco, Paraguay.

Image courtesy of Peter Halasz.Life Environments Page 20

Altitude• Biomes change with elevation in a manner similar

to their change with latitude.

Holdridge life zone classification scheme.

Life EnvironmentsLeft-hand image courtesy of Wikimedia Commons.

Right-hand image courtesy of NASA. Page 21

Rain Shadow• A region that is more arid than it would be

otherwise because it is downwind of mountains.– Rising air cools and tends to release moisture.– Descending air warms and tends to retain

moisture.

Schematic of a mountain range forming a rain shadow. The Tibetan Plateau is an excellent example of

a rain shadow.

Life Environments Image courtesy of National Park Service. Page 22

Monsoon• A pronounced seasonal wind pattern caused by

the differences between land and water in heat capacity and depth of heat penetration:– In summer, hot air rising over the land generates

low pressure that draws moist air from the sea.– In winter, hot air rising over the sea generates low

pressure that draws dry air off the land.• A• Affects rainfall patterns in

Australia, southeast Asia, India, northwestern Mexico and the U.S. Southwest, western sub-Saharan Africa, and Brazil.

Summer monsoon thunderstorm, Canyonlands

National Park, Utah.

Life EnvironmentsImage copyright © 1999-2008 Michael Pidwirny,

University of British Columbia-Okanagan. Page 23

Ocean Surface Currents• Generated by prevailing surface winds and the

Coriolis Effect.– Flow in gyres that are clockwise north of the

Equator and counterclockwise south.

Life Environments Image courtesy of NASA. Page 24

Antarctic Circumpolar Current• Created by strong westerly winds blowing across

the continuous seaway that surrounds Antarctica.– Earth’s longest and probably largest ocean current.– Contributes to the frigidity of Antarctica by

preventing any approach of warm ocean water.

Life Environments Image courtesy of NOAA. Page 25

Marine Food Webs• Based on plankton,

which are floating aquatic life.– Phytoplankton:

Photosynthetic plankton, mostly single-celled algae.

– Zooplankton: Animal or animal-like plankton.

• Include nekton— swimming animals—and benthos—bottom-dwelling life.

Arctic marine food web.

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Marine Environments• Limiting factors include light, temperature, water

depth, water movement, salinity and dissolved O2.– The huge heat capacity of water creates uniform

conditions within immense volumes of the ocean:• The intertidal zone, periodically dry, is home to algae,

sponges, mollusks, starfish, and crabs.• The neritic zone, lying above the continental shelf to

about 650 feet depth, is home to algae, crustaceans and many fishes.

• The pelagic zone, or open ocean, consists of a 650-foot deep photic zone lying above an aphotic zone.

– Light penetrates the photic zone, home to phytoplankton, bony fish, sharks and whales.

– The pitch black aphotic zone is home to a unique fauna. Dead organisms raining down is the main food source.

Marine Biogeography• Water temperature controls the spatial patterns of

phytoplankton and reef-building organisms and, through them, the rest of marine life.– Some groups, such as the reef-building corals and

calcareous nannoplankton prefer warmer water.– Other groups, like the diatoms, prefer colder water.

Life Environments Image courtesy of NOAA. Page 27

◄ The red dots show the location of major

stony coral reefs

Life Environments Image courtesy of U.S. Geological Survey. Page 28

Salinity• Dissolved salt content of natural water.

– In seawater, normally 3 to 4%.• Brackish water is less saline than normal seawater.• Hypersaline water is more saline than normal seawater.

– Salinity fluctuations in bays and lagoons limits the number of species in such environments.

Louisiana saltwater marsh. ►

Life Environments Image courtesy of NASA. Page 29

Thermohaline Circulation• A connected set of surface and bottom currents

that circulate oceanic water on a global scale, supplying oxygen to the deep ocean.– A complete loop takes about 2000 years.– Driven by water density differences:

• Lower temperature and higher salinity increase density.

Image courtesy of Wikipedia.Life Environments Page 30

Fresh Water• Natural water with a salinity of less than 0.5%.

– Occurs in streams and lakes.– Creates a difficult environment for life:

• Osmosis causes a net movement of water into cells, potentially causing them to burst.

• Currents sweep away floating organisms.

◄ A rocky stream in Hawaii.