WHAT ARE THE COMPONENTS OF THE BIOSPHERE?

CHAPTER 42

ECOLOGISTS STUDY HOW ORGANISMS INTERACT WITH THEIR ENVIRONMENT AT SEVERAL LEVELS

Ecologists study environmental interactions at several levels:

Organism-how one kind of organism meets challenges of environment. E.g. adaptation of a clam to extreme temperatures.

Population-an interbreeding group of individuals belonging to same species and living in same geographic area. E.g. study of growth rate in clams living near the hydrothermal vent.

Community-all the organisms (all populations of different species) that inhabit a particular area. E.g. all organisms found near the hydrothermal vent. More focus on interactions e.g. predator-prey.

Ecosystem-includes all life forms in a certain area and all the non-living factors as well.

Abiotic components-non-living component of the ecosystem e.g. temperature, water, air.

Biotic component-living component of the biological community; e.g competition, predation.

THE BIOSPHERE IS THE TOTAL OF ALL OF EARTH’S ECOSYSTEMS

Biosphere-the global ecosystem-sum of all the planet’s ecosystems. Most complex level in ecology.

Features of biosphere:

It’s self-contained except deriving energy for photosynthesizers from sunlight.

Its patchy e.g. distribution of continents and oceans.

PHYSICAL AND CHEMICAL FACTORS INFLUENCE LIFE IN THE BIOSPHERE

Solar energy-powers nearly all terrestrial and shallow-water ecosystems. E.g. photosynthesis.

Water-essential to all life. E.g. Organisms have ways of preventing drying out in terrestrial ecosystems-cuticle.

Temperature-important effect on metabolism. E.g. adaptations to live outside the normal body temperature; resistant enzymes.

Wind-reason for patchiness in ecosystems.

Other abiotic factors-soil structure, pH, nutrient, unpredictable disturbances (fire, hurricanes etc).

ORGANISMS ARE ADAPTED TO ABIOTIC AND BIOTIC FACTORS BY NATURAL SELECTION

Organism’s ability to survive and reproduce in a particular environment is a result of natural selection.

A species is present in a location due to 2 reasons:

The species evolved in that location.

The species got dispersed to this location and it could survive there.

REGIONAL CLIMATE INFLUENCES THE DISTRIBUTION OF BIOLOGICAL COMMUNITIES

Solar radiation varies with latitude

PREVAILING WIND PATTERNS

Doldrum-an area of calm or very light winds near the equator, caused by rising warm air.

Trade winds-the movement of air in the tropics. Blow from east to west.

Prevailing winds-major global air movements that result from the combined effects of the rising and falling of air masses and Earth’s rotation.

Because Earth is spherical, its surface moves faster at the equator than at other latitudes.

OCEANIC ZONES

OCEANIC COMMUNITIES & ZONES

• Estuary-area where a freshwater stream or river merges with the ocean. Most productive biome.

• Wetland-ecosystem that is intermediate between an aquatic ecosystem and a terrestrial one. Usually has soil saturated with water, either periodically or permanently.

• Intertidal-where water meets land. Area is flooded by high tides then left dry at low tides every 12 hours.

Pelagic zone-open ocean; communities of highly motile animals e.g. fish, squids.

Phytoplankton-diverse algae and cyanobacteria drift passively in the pelagic zone. Ocean’s major photosynthesizers.

Zooplankton-animals that drift in pelagic zone and most float. Consume phytoplankton.

Benthic zone-seafloor.

Photic zone-small portion of ocean water and bottom into which light penetrates and in which photosynthesis occurs.

Aphotic zone-under photic zone; dark region. Most extensive part of the biosphere.

Continental shelves-submerged parts of the continents.

Coral reefs-found in warm tropical waters above continental shelf. Dominated by hard skeletal structures secreted primarily by cnidarians.

FRESHWATER BIOMES INCLUDE LAKES, PONDS, RIVERS, STREAMS AND WETLANDS Light has significant effect on freshwater biomes.

Temperature also has profound effect on freshwater communities.

Many lakes and ponds are affected by large inputs of nitrogen and phosphorus from sewage runoff and fertilizers from agriculture.

Wetlands are the richest of biomes in terms of species diversity.

Their ecological and economic value has led to protection and restoration of wetlands.

TERRESTRIAL BIOMES REFLECT REGIONAL VARIATIONS IN CLIMATE

North

America

South

America

Europe

AsiaAfrica

Oceania

Arctic

A type of biological community not a specific assemblage of species characterizes each biome. E.g. organisms adapted to arid conditions will be found in desert areas.

How are Biomes named?1. Climatic features 2. Predominant vegetation 3. Microorganisms 4. Animals adapted to that environment

Distribution of biomes depends on:1. Climate 2. Temperature 3. Rainfall

TROPICAL FOREST Tropical forests-occur in equatorial

areas where temperature is warm and days are 11-12hours long year-round.

Rainfall quite variable and determines the vegetation that grows.

Most complex of all biomes having enormous numbers of different species.

Vertical stratification provides many different habitats.

Soils are poor because high temperatures and rainfall lead to rapid decomposition and recycling rather than build up of organic material.

Human impact on tropical forests is a great concern: Clear forest for timber. Burn forest. Farm forest than abandon it. Mining.

Recovery of rainforest very slow due to nutrient-poor soil.

Consequences of deforestation: Lose species and productivity. Degradation of soil and water resources. Fragmentation of landscape. Hindrance to regulation of climate and cycles of nutrients

and water and gases.

SAVANNAS Savanna-biome dominated by

grasses and scattered trees.

Central South America, central and South Africa.

Simple in structure c.f. tropical forests.

Frequent fires (human activity and lightning) and grazing animals inhibit further invasion by trees.

Dominant plants are fire adapted.

Dominant animals-insects, mice. Moles, squirrels, worms, giraffes, zebras, cheetahs, lions.

DESERTS Deserts-driest of all terrestrial biomes,

characterized by low and unpredictable rainfall.

Both cold and hot deserts.

Sahara desert, Kalahari in Africa.

Plant community-cacti and deep-rooted shrubs.

Periods of rainfall followed by blooms of annual plant.

Animal community-seed-eating ants, birds and rodents. Also lizards, snakes and hawks.

CHAPARRAL

Chaparral-region of dense, spiny shrubs with tough, evergreen leaves.

Occurs in midlatitudinal coastal areas.

Plant community-perennial shrubs and annual plants.

Requires fires for long-term maintenance.

Animal community-deer, fruit-eating birds, seed-eating rodents, lizards and snakes.

TEMPERATE GRASSLANDS Temperate grasslands-share characteristics of tropical savannas, but

they are mostly treeless, except along rivers or streams.

Found in regions of relatively cold winter temperatures.

Keys to the persistence of most grasslands are seasonal drought, fires and grazing by large animals all of which inhabit the growth of woody plants.

Animal community-pronghorn, zebras, horses, sheep.

Amount of rainfall influences height of vegetation.

Temperate deciduous forests-grow throughout midlatitudinal regions where there is sufficient moisture to support growth of large trees.

Broadleaf, deciduous trees (oak, maple) characterize this biome.

Temperatures range from very cold in winter to very hot during summer.

Rainfall is relatively high annually.

Soil is rich in organic and inorganic nutrients.

Animal community-birds, foxes, black bears, mice, squirrels.

Temperate Deciduous Forest

CONIFEROUS FORESTS

Coniferous trees-forests with cone-bearing evergreen trees such as spruce, pine, fir and hemlock.

Found at cool, high elevations in more temperate latitudes.

Soil usually nutrient-poor, thin and acidic.

Conifers with fire-resistant cones and seeds colonize recently burned areas.

Animal community-squirrels, grizzly bears, wolves, migratory birds.

TUNDRA Tundra-biome at the northernmost limits of plant growth and

at high altitudes, characterized by dwarf woody shrubs, grasses, mosses and lichens.

Climate is often extremely cold with little light for long periods of time.

Absence of trees due to cold air, high winds and permafrost (soil or rock < 0oC).

Animals survive by good insulation-rodents, foxes, and insects.