Ecosystems and Communities Chapter 4

The Role of Climate - Sec. 4.1 Organisms vary in their adaptations to temperature, rainfall, and other environmental conditions. Species also vary in their tolerances for conditions outside their normal ranges. Weather – day to day conditions of the Earth’s atmosphere at a particular place and time. Climate – average, year to year conditions of temperature and precipitation in a particular region.

The Greenhouse Effect The atmosphere traps heat energy and maintains Earth’s temperature range. Top three gases: carbon dioxide, methane, water vapor. Sunlight enters the atmosphere as short wavelength radiation and is converted to long wavelength heat which can not escape back out into space. Without the greenhouse effect the Earth would be too cold to sustain life.

The Effect of Latitude on Climate Because Earth is a sphere that is tilted on its axis, solar radiation strikes the surface at an angle that varies throughout the year. The further you move away from the equator the more solar radiation varies during the seasons. This divides the Earth into three main climate zones: 1. Polar – cold areas where light hits at low angle

2. Temperate – affected by tilt of Earth so seasonal change is great 3. Tropical – near equator from 23.5 degrees north to 23.5 degrees south.

Heat Transport in the Biosphere Because the sun is directly overhead year round at the equator climatic conditions vary very little. Heat Transport in the Biosphere Unequal heating of the atmosphere drives winds and ocean currents. Warm air rises and cold air sinks. As warm air rises it is replaced by heavier cold air – creates prevailing winds. Cold water at the poles sinks and flows toward the equator where it warms and rises. These air and water movements transfer heat throughout the world.

Continents and other land masses can also affect winds and ocean currents. Winds over the oceans influence currents. As air rises over mountains, it cools and often loses its moisture as precipitation. This causes a dry area on the leeward side of the mountains = Rain Shadow Effect

Rain Shadow Effect

What Shapes an Ecosystem? – Sec. 4.2 Biotic Factors - biological influences affecting an organism in its environment - all of the living organisms in an ecosystem Abiotic Factors - physical, or nonliving, factors that affect an organism in an ecosystem - climate, nutrient availability, soil type, sunlight, rainfall, etc.

Habitat = where an organism lives Together, biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which the organism lives. Niche - an organism’s habitat and its role in the habitat - includes biotic and abiotic factors, its role in the food web, its physical tolerances, its reproductive methods, etc.

- no two species can share the same niche. in the same habitat. Fig - Many species have similar, but slightly different niches - Fundamental niche – the complete niche that a species could occupy - Realized niche – the niche that a species occupies when in competition with other species.

Community Interactions - refers to interactions between organisms A. Competition - occurs when organisms of the same or different species try to use the same resource in the same place at the same time. - Competitive Exclusion Principle - no two species can occupy the same niche in the same habitat at the same time

Resource partitioning in Anolis lizards. A. distichus A. insolitus

B. Predation - where one organism eats another - predator vs. prey

C. Symbiosis - relationships in which two species live closely together. A) Mutualism - both species benefit

B) Commensalism - one organism benefits and the other has no positive or negative effect - oxpeckers on grazers - barnacles on whales

C) Parasitism - one organism lives on or in another organism and harms it. - host vs. parasite

Ecological Succession - ecosystems constantly change in response to natural and human disturbances. - results in a replacement of one community of species by another community - as organisms live in an area they make the area better suited to other species - Primary Succession - when succession occurs where no soil previously exists - lava flows, sand dunes, bare rock, etc. - pioneer species = first species to populate

- lichen are often pioneer species - composed of a fungus and algae - begin breaking down rock and forming soil - prepare the area for small grasses or herbs, which further prepare the area for other species Secondary Succession - when disturbance changes an existing community but does not remove the soil - after fires, cutting forests, abandoned farmland

Secondary Succession

Primary Succession

Alders to cottonwood

Spruce into Forest

Mount Saint Helens

- organisms are adapted to certain biomes Biomes – Sec. 4.3 * complex of terrestrial ecosystems that cover a large area and is characterized by certain soil and climate conditions and particular communities of plants and animals. - organisms are adapted to certain biomes - an adaptation is an inherited characteristic that increases an organism’s ability to survive and reproduce. - each species has a range of tolerance for every environmental factor - microclimate is often very important (insert graph of Law of Tolerances)

Terrestrial Biomes

Climatograph

1. Tropical Rain Forest (pg. 100) 2. Tropical Dry Forest (pg. 100) 3. Tropical Savanna (pg. 101) 4. Desert (pg. 101) 5. Temperate Grassland (pg. 102) 6. Temperate Woodland and Shrubland 7. Temperate Deciduous Forest (pg. 103) 8. Northwestern Coniferous Forest (pg. 103) 9. Boreal Forest (Taiga) (pg. 104) 10. Tundra (pg. 104)

Aquatic Ecosystems – Sec. 4.4 - are grouped according to abiotic factors which affect them. - determined primarily by depth, flow, temperature, and chemistry of the water - depth determines light penetration - water chemistry refers mostly to the amount of dissolved chemicals in the water – salts, nutrients, and oxygen - water covers approximately 75% of Earth’s surface -about 3% of Earth covered by fresh water

Aquatic Ecosystems

Freshwater Ecosystems - divided based on if water is flowing or still 1. Flowing-water ecosystems - rivers and creeks - change along their length - headwaters often cold and turbulent with lots of dissolved oxygen but little plant life (trout) - further down soil builds up, water slows, more plants grow (catfish) - organisms are well adapted for speed of water

2. Standing-water ecosystems - lakes and ponds - still water is good habitat for plankton * tiny, free-floating or weakly swimming organisms in both freshwater and saltwater environments * phytoplankton – single-celled algae – base of most aquatic ecosystem food chains * zooplankton – planktonic animals which feed on the phytoplankton

Freshwater Pond

3. Freshwater Wetlands - ecosystems in which water either covers the soil or is present at or near the surface of the soil for at least part of the year - often very productive a. bogs – dominated by sphagnum moss - form in depressions where water gathers – often acidic soils/water b. marshes – shallow wetlands along rivers - often contain cattails, reeds, rushes

c. swamps – water slowly flows through - often look like flooded forests Estuaries * wetlands where rivers meet the sea - mixed fresh and salt water - affected by rise and fall of tides - often shallow, so they support many producers and are extremely productive - detritus feeds many of the lower levels of the food chains - important spawning and nursery areas

a. Salt marshes - temperate zone estuaries dominated by salt-tolerant grasses above the low-tide line and seagrasses below * much of Texas Coast b. Mangrove swamps - tropical wetlands dominated by salt- tolerant trees called mangroves - seagrasses below low-tide line - valuable nurseries for fish and shellfish * coast of Everglades N.P.

Estuaries

Marine Ecosystems – pg. 109

Marine Ecosystems * Photic Zone – area where light penetrates - photosynthetic producers * Aphotic Zone – below light penetration - chemosynthetic producers and detritus 1. Intertidal zone - area between high and low tide - organisms adapted to being exposed for part of the day - clear zonation of organisms

Marine Ecosystems

2. Coastal Ocean - extends from low-tide mark to outer edge of continental shelf - often all in the photic zone - kelp forests 3. Coral Reefs - warm, shallow tropical waters - coral animals’ hard calcium carbonate skeletons make up the reef base 4. Open Ocean - low productivity, but huge area makes it important for worldwide photosynthesis

5. Benthic Zone - ocean floor ecosystem - usually depends on detritus “raining down” - benthos – organisms which live on the ocean floor

Characteristics of Populations 1. Population Density - number of individuals per unit of area 2. Geographic Distribution - range - the area inhabited by a population 3. Growth Rate - depends on birth rates, death rates, and the number of individuals moving into or out of a population

Populations in nature grow in two ways: 1. Exponential Growth - occurs in populations with abundant space, resources, and few predators or disease - individuals in a population reproduce at a constant rate. - at first population grows slowly, but steadily increases at an accelerating speed.

Exponential Growth – Whooping Cranes

2. Logistic Growth - after a period of exponential growth, resources become limited and population growth slows or stops. - slows due to decrease in birthrate, increase in death rate, or both - eventually the population reaches a maximum size that the environment can support = Carrying Capacity

Logistic Population Growth

Limiting factors cause population growth to decrease. Density-Dependent Factors - limiting factors that depend on population size - become limiting only when the population density reaches a certain level and as population grows the factor becomes more limiting. * competition, predation, parasitism, disease Density-Independent Factors - affect all populations in similar ways, regardless of population size * weather, natural disasters, seasonal cycles, and human activities

Human Population growth has historically been exponential. Age-structure diagrams give a view of what a population is like now and what might happen in it in the future.