Chapter 4 Ecosystems and Communities

1. The role of Climate 4-1
1. What is Climate?
1. Weather - day -to-day condition of Earth's atmosphere at a particular time and place. Cloudy one day and clear the next day…
2. climate - average, year-after-year conditions of temperature and precipitation in a particular region.
3. Climate is caused by the interplay of many factors, including the trapping of heat by the atmosphere, latitude, the transport of heat by winds and ocean currents, and the amount of precipitation that results. The shape and elevation of landmasses also contribute to global climate patterns.
2. Solar Radiation
1. The interplay of the ocean and atmosphere, combined with the presence of landmasses, help create Earth's climate.
2. The Greenhouse Effect
1. This natural circumstance, helps maintain Earth's temperature range.
2. CO₂; CH₄ (methane); H₂O vapor; and a few other atmospheric gases trap heat energy and maintain Earth's temperature range.
3. Heat/energy enters atmosphere, but not all heat leaves atmosphere…like a greenhouse.
3. The Effect of Latitude
1. As a result of differences in the angle of heating, Earth has 3 main climate zones:

• Polar
• Tropical
• temperate

1. Polar zones - cold areas where the sun's rays strike the Earth at a very low angle.

• 66.5⁰ - 90⁰ North and South

1. Tropical zone - near equator, sun's rays are directly overhead at noon at the solstice.

• 23.5⁰ North - 23.5⁰ South

1. Temperate zone - between polar and tropic

• Most affected by the angle of the Sun …so experience wide range climate depending on season.

1. Heat Transport in the Biosphere
1. Together, winds, ocean currents, and landmasses influence temperature and precipitation, which in turn create Earth's climate.
2. Unequal heating of Earth's surface drives winds and ocean currents, which transport heat throughout the biosphere.
3. Winds form because warm air tends to rise and cool air tends to sink. …air absorb heat (near equator) will rise and polar air will sink toward the ground.
4. This exchange cause air currents, wind that move heat throughout the atmosphere.
5. Same effect hot/cold rise/sink water exchange …creates ocean currents.
6. Ocean currents also interact with air currents.
7. Rotation of the Earth further affects winds and ocean currents, causing them to travel in curved or circular paths.
8. Continents and other landmasses can also affect winds and ocean currents.

1. What Shapes an Ecosystem? 4-2
1. Biotic and Abiotic Factors
1. biotic factors - biological influences on organisms within an ecosystem.
1. Ecological community
2. I.e.: biotic factors influencing a bullfrog might be:…..
2. Abiotic factors - physical, or nonliving, factors that shape the ecosystem.
1. Climate, including temperature, precipitation, and humidity.
2. Wind
3. Nutrients available
4. Soil type
5. Sunlight
6. I.e.: dry heat creates thirst.soil may determine water retention...water needs.
3. Together, biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which the organism lives.
2. The Niche - the full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions.
1. No two species can share the same niche in the same habitat…(for long)
3. Community Interactions - can powerfully affect an ecosystem. (competition; predation and symbiosis)
1. Competition - when organisms of the same or different species attempt to use an ecological resource in the same place at the same time.
1. Resource - any necessity of life, i.e.: broad oak leaf...sunlight etc..
2. Competitive exclusion principle - no two species can occupy the same exact niche in the same habitat at the same time.
2. Predation- interaction where one organism captures and feeds on another organism.
1. Predator - kills and consumes
2. Prey - organism turns into someone's lunch
3. Prey and Predator relationship is dynamic changing availability of prey and/or predator.
3. Symbiosis - any relationship in which 2 species live closely together
1. Mutualism - both species benefit from the relationship

• Flowers and insect…Yucca plant and Yucca moth.

1. Commensalism - one member of the association benefits and the other is neither helped nor harmed.

• Barnacles on whales.

1. Parasitism - one organism lives in or on another organism, obtaining from its host part of all of its nutritional needs.

• Fleas, lice, ticks, tapeworms etc..
• Most effective parasites don't kill their hosts.

1. Disturbance and Succession
1. Ecological succession - Ecosystems are constantly changing in response to natural and human disturbances.
2. As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community.
3. Causes of Succession - slowly ( freshwater pond) or quickly (fire or hurricane)
1. Some plants (pines) depend on periodic fire disturbances
4. A case study whale-fall community in deep ocean ecosystem
1. begins with large whale dies and sinks to barren ocean floor. ..carcass attracts scavengers and decomposers… hagfish; sharks feed on decaying meat.
2. Within a year…most of tissues have been eaten. Smaller animals are supported: fishes; crabs etc.. the nutrients enter into sediment surrounding whale remains….great digs for sediment dwellers like marine worms.
3. When only whale's skeleton remains. 3^rd community moves in. Heterotrophic bacteria begin to decompose oils inside bones. This then releases chemical compounds that serve as energy source for the chemosynthetic autotrophs….so now who moves in…chemoshynthetic bacteria…that now support other organisms…mussels, limpets, snails, worms, crabs, clams that live off bones and sediment surrounding whale remains.
5. Primary and Secondary Succession -gradual over years
1. i.e.: Hawaii typically begins with lichens on volcanoes
2. primary succession - when succession occurs on newly exposed geological surfaces that are not significantly modified by organisms.
3. Secondary succession - when a disturbance destroys a community without destroying the soil.

• I.e.: agricultural land is abandoned; fires;

1. Climax communities - when succession has ended with a mature, stable community with relatively small changes…

• I.e.: forests in Northwest; deserts; swamps of Alabama…etc..

1. Land Biomes 4-3

Biome - is a geographical region that contains a characteristic assemblage of plants and animals.

1. Climate and Biomes

• Temperature
• Precipitation

1. The Major Biomes
1. The world's major land biomes are each defined by a unique set of abiotic factors, particularly climate-
2. Tropical Rain Forest -
1. home to more species of all other land biomes combined
2. canopy - leafy top of trees 70 meters above forest floor.
3. Understory - in the shade of the canopy, 2^nd layer of shorter trees and vines.
4. Abiotic factors - hot and wet year round; thin; nutrient -poor soil.
5. Dominant plants - broad leaf evergreen trees; ferns; woody vines; climbing plants.
6. Dominant wildlife - insects, diverse fruits, ground and tree dwelling life.
7. Geographic distribution: near equator…around the world.
3. Tropical Dry Forest
1. Grow in regions where rainfall is highly seasonal rather than year-round.
2. During the dry season, nearly all the trees drop their leaves to conserve water.
3. Deciduous - tree that sheds its leaves during a particular season each year.
4. Abiotic factor - warm year round; alternating wet/dry seasons; rich soils subject to erosion.
5. Dominant plants - tall, deciduous ….succulents
6. Dominant Wildlife - variety of large herbivores mammals; carnivores; termites; insect eaters
7. Wildlife…many species migrate to wetter areas during the dry season.
8. Geographical distribution - Africa; South and Central America Mexico, India; Australia and tropical islands.
4. Tropical Savanna
1. More rainfall than deserts, but less than tropical dry forests.
2. Characterized by continual cover of grasses, some trees
3. Abiotic factors - warm temperatures, seasonal rainfall; compact soil; frequent fires set by lightning.
4. Dominant plants - tall; perennial grasses; sometimes drought-tolerant and fire- resistant trees or shrubs.
5. Dominant wildlife - large herds of grazing herbivores that migrate vast distances during the dry season; carnivores such as lions and hyena; vultures and other scavengers.
6. Geographic distribution - large parts of eastern Africa, southern Brazil; northern Australia, and large regions of India and Pakistan.
5. Desert -
1. Annual rain forest < 25 cm.
2. Vary according to elevation and latitude
3. Experience extreme temperature changes
4. Plants and animals can tolerate temperature changes
5. Abiotic factors - variable temperatures; low precipitation; soils rich in minerals but poor in organic material.
6. Dominant plants - great diversity, succulents (cacti) also plants with short growth cycles.
7. Dominant wildlife - jack rabbits; rodents; foxes; reptiles; scorpions; insects; and birds.
8. Geographic distribution - Africa, Asia, Middle East, SW USA; South America and Australia.
6. Temperate Grassland
1. Rich mix of grasses with fertile soils,

• Plains and prairies

1. Periodic fire and heavy grazing by large herbivores maintain plant community.
2. Abiotic factors - warm to hot summers; cold winters; moderate seasonal precipitation; fertile soils; occasional fires.
3. Dominant plants - lush, perennial grasses and herbs; most are resistant to drought, fire, and cold.
4. Dominant wildlife - large grazing mammals; carnivores; prairie dogs and other rodents.
5. Geographic distribution - central Asia; North America, Australia; central Europe; Africa and plateaus of South America.

1. Temperate Woodland and Shrubland
1. mix of scrubby woods and woody shrubs that grow within a semiarid climate
2. chaparral - communities are dominated by shrubs
3. growth of dense, low plants that contain flammable oils makes fires a constant threat.
4. Abiotic factors - hot dry summers characterized by drought; cool; moist winters; thin; nutrient-poor soils; periodic fires.
5. Dominant plants - woody evergreen shrubs with small, leathery leaves; fragrant; oily herbs that grow during winter and die in summer.
6. Dominant wildlife - coyotes; ground-dwelling herbivores; a variety of birds; snakes and amphibians.
7. Geographic distribution - western coasts of N and S America, areas around Mediterranean Sea; South Africa, and Australia.
2. Temperate Forest
1. mixture of deciduous and coniferous

• coniferous - seed bearing cones and leaves shaped like needles

1. cold winters stop growth for months
2. fall, deciduous leaves fall and spring, small plants come up
3. humus - abundant organic matter and nutrients are stored in a layer of decaying leaves and twigs on forest floor.
4. Abiotic factors - cold to moderate winters, warm summers; Year round precipitation; and fertile soils
5. Dominant plants - broadleaf deciduous tress; flowering shrubs; herb; lichen; mosses and ferns
6. Dominant wildlife - Mostly nut and acorn feeders, like squirrels; omnivores like raccoons and skunks.
7. Geographic distribution - E and NW USA; southern Canada; most of Europe; and parts of Japan, China; and Australia.

1. Boreal Forest - (boreal = north [Greek])
1. Along the northern edge of temperate zone dense evergreen forest of coniferous trees.

• Taiga - biomes called boreal forests cold winters stop growth for months

1. Winters are bitterly cold, but summers are mild and long enough to allow the ground to thaw.
2. Abiotic factors - long, cold winters; short, mild summers; moderate precipitation; high humidity; acidic; nutrient-poor soils.
3. Dominant plants - needleleaf coniferous trees such as spruce; some broadleaf deciduous trees; small berry-bearing shrubs.
4. Dominant wildlife - fur-bearing predators like lynx and members of the weasel family; small herbivorous mammals; moose and other large herbivores; beavers; songbirds and migratory birds.
5. Geographic distribution - North America; Asia; and northern Europe.

1. Tundra
1. Permafrost - layer of permanently frozen subsoil.
2. During short, cool summer, the ground thaws to a depth of a few cm and becomes soggy and wet.
3. In winter, topsoil freezes again.

• This cycle of thawing and freezing, which rips and crushes plant roots, is one reason that tundra plants are small and stunted.

1. Cold temperatures, high winds, the short growing season, and unaccommodating soils also limit plant height.
2. Abiotic factors - strong winds; low precipitation; short and soggy summers; long, cold, and dark winters; poorly developed soils; permafrost.
3. Dominant plants - ground hugging plants such as mosses, lichens, sedges and short grasses.
4. Dominant wildlife - a few resident birds and mammals that can withstand the harsh conditions; migratory waterfowl, shore birds, and caribou; lemmings and other small rodents.
5. Geographic distribution - northern North America; Asia; and Europe.

1. Other Land Areas
1. Polar Ice - icy polar regions that border the tundra
1. Cold year-round, dark winters, subject to fierce winds.
2. Thick layers of snow and permanent ice caps with no soil make it impossible for plants to grow and difficult for land animals to find food.
3. Lichens and mosses; algae (with fungus becoming lichen)
4. Arctic animals; polar bears, seals, musk ox, Artic foxes, snowy owls, insects and mites
5. Antarctica penguins and marine mammals.
2. Mountain Ranges
1. found on every continent
2. can be considered climatic and biological islands because of elevation changes. (biomes change with elevations)

1. Aquatic Ecosystems 4-4

• -3/4 of the Earth's surface is covered with water
• unlike land biomes, aquatic ecosystems are not grouped geographically, but by depth of water.
• Primarily the depth, flow and chemistry of the overlying water determine aquatic ecosystems.

1. Freshwater Ecosystems
1. Freshwater ecosystems can be divided into 2 main types: flowing-water ecosystems and standing-water ecosystems.
2. Flowing-Water Ecosystems- rivers, streams creeks and brooks.
1. Adaptations like hooks, suckers and body shapes to flowing water.
2. Near the source of the spring, turbulent water, plenty of O₂, little plant life.
3. Sediments build up as flows downhill, plants can be established.
4. River farther down meanders where turtles, beavers, river otters can thrive.
3. Standing-Water Ecosystems- lakes, ponds most common
1. plankton - general term for tiny, free-floating weakly swimming organisms
2. plankton can occur in freshwater and saltwater
3. phytoplankton - single-celled algae supported by the nutrients in the water and form the base of many aquatic food webs
4. zooplankton- feed on the phytoplankton
5. freshwater plankton- about the size of dust particles, fed upon by fishes, frogs, turtles, birds,
2. Marine Ecosystems
1. photic zone- 30 to 200 meters deep (thin)
1. Photosynthesis is limited to this well-lit upper layer.
2. Algae and other producers grow
2. aphotic zone- permanently dark
1. chemosynthetic autotrophs are the only producers that can survive
3. Zones and Communities
1. Marine biologists also divide the ocean into vertical zones based on depth and distance from shore.

• intertidal zone
• nertic zone
• open ocean

1. benthic zone covers the ocean floor and is therefore, not exclusive to any of the other marine zones.

1. Intertidal Zone
1. organisms are exposed to extreme changes to their surroundings
2. battered by waves, exposed to air, sun- then underwater.
3. Competition among organisms in rocky intertidal zones often leads to zonation.
4. Zonation is the prominent horizontal banding of organisms that live in a particular habitat. I.e.: stripes of black algae; barnacles; blue mussels then green algae.
2. Neritic Zone
1. extends from the low-tide mark to the end of the continental shelf
2. usually gets light to support organisms …especially rich in plankton and other aquatic organisms.
3. Coral reefs: calcium carbonate skeletons of coral animals

• Warm, tropical waters

1. Kelp forests: temperate coastal areas of California and Pacific Northwest

• Kelp- giant seaweed grow quickly- support complex food web of snails, sea urchins sea otters, seals, whales, and small fish.

1. Open Ocean - (Oceanic zone)
1. begins at edge of continental shelf and extends outward
2. largest marine zone (90% of surface area of the world's ocean)
3. deep- high pressure; frigid temperatures total darkness.
4. Low levels of nutrients- food webs are long, productivity low
5. Because of the enormous area , most of the photosynthetic activity on Earth occurs there.
6. Fish; marine mammals; sea birds, rely on these zones.
2. Benthic Zone
1. benthos - organisms live attached to or near the bottom of ocean
2. sea stars, anemones, marine worms etc…
3. benthic ecosystems often depend on food from organisms that grow in photic zone, particularly the producers.
4. Clams, sea cucumbers are attached to the bottom feed on dead organic material (detritus) that drifts down.
5. Deep-sea vents have chemosynthetic are the primary producers.

1. Wetlands
1. ecosystem where roots of plants are submerged under water at least part of the year.
2. wetlands are enormously productive ecosystems, serving as breeding and nursery grounds for insects, fishes, amphibians and birds.
3. buffer and reserve water that play vital role in water cycle by naturally purifying the water.
4. salt marshes - flat, muddy , salt-tolerant grasses above low-tide line and sea grasses under water.
5. mangrove swamps - warm climates- salt tolerant, woody plants low O₂.
1. mangroves trees are adapted to low oxygen having roots emerge from the water..

• elaborate root systems trap sediments, causing soil to accumulate behind the plants.

1. Estuaries - ecosystem which a freshwater source, usually mouth of a river or stream, meets the ocean
1. subject to rise and fall of ocean tides
2. shallow, photic zone
3. abundant plants, algae, bacteria
4. because of the abundant organic material produced, many food webs are based on detritus.
5. spawning and nursery grounds etc. ; oysters, shrimp crabs, birds nest, feed and rest during migrations.