Chapter 6 Ecosystem Balance

Ecosystem Balance 6.1 Relationships in the Ecosystem 6.2 Ecological Succession 6.3 Stability in the Ecosystem 6.4 Land Biomes

6.1 Relationships in the Ecosystem Objectives Explain the relationship between the population sizes of predator and prey. Define symbiosis and describe several symbiotic relationships.

Relationships in the Ecosystem A complex web of relationships exist among all the species in an ecosystem. Scientists study these relationships by: Studying how two populations interact with one another. Expanding the knowledge they have gained to other parts of the ecosystem.

Predator and Prey One of the relationships ecologists study is that of predator and prey. Define Predator. Define Prey Examples

Predator and Prey

Predator and Prey The sizes of predator and prey populations are closely linked. Figure 6.1 p. 89 Prey experience populations cycles. A predator’s populations cycle mimics that of its prey.

Parasitism Some animals do not kill the prey they feed on. Parasitism-an organism that feeds on the tissue or body fluids of another organism Host-the organism the parasite feeds off of Examples

Parasites-Tapeworms and Roundworms

Symbiosis Symbiosis-a relationship in which two species live closely together Three types: Parasitism-one is helped and the other is harmed (typically) Commensalism- one organism benefits and the other is neither helped or harmed Examples Mutualism-both organism benefit

Commensalism

Mutualism

Questions What is the relationship between the population sizes of predator and prey. Define Symbiosis What are some examples of symbiotic relationships?

6.2 Ecological Succession

Objectives Contrast primary and secondary succession. Describe the sequence of ecological succession in a lake and on an island.

Ecological Succession Organisms affect their environment Example: Plants  Soil Changes are not always beneficial Old niches are replaced by new niches. Other forces can cause change in the environment. Example: Forest Fire

Ecological Succession As environment change the communities living in that environment change as well. In many cases different communities follow one another in a definite pattern, this is called succession.

Volcano Eruption A volcano erupts leaving the land covered in bare black rock…it is lifeless. Does it stay this way?

Volcano Eruption (cont) Almost immediately organisms begin to inhabit the area.

Primary Succession Define Primary Succesion Examples: Cooled lava fields and exposed rock from retreating glaciers.                                                                                                                                                 

Primary Succession Primary succession is an orderly process. Follows the same general pattern in most ecosystems.

Step 1 Colonization by new organisms and formation of soil from exposed rock. On land this is done by lichens. Define lichens. Lichens can live on bare rock.                                                                                                                                                 

Step 1 (cont) Lichens secret acids that break down the rock and form organic material by photosynthesis. Weathering also breaks down rocks. Soil is formed by the actions of the lichens and weathering.

Pioneer Community Lichen Community First community to colonize the area.

Step 2 Once soil is formed, grasses and other small plants begin to grow. Root growth and accumulation of dead leaves  Soil formation Plants grow dense  lichen disappear

Grass Community Survives for many generations and makes the soil deeper and more fertile. Soil is deep enough  Growth of nonwoody plants with deep roots (Heath Mat). These plants are taller and shade out the grasses. Since the grass/shrub community is not diverse a small disturbance may cause drastic change.

Pines and other tress Pines or other trees with shallow roots are next. Trees shade out the heath mat.                       

Broadleaf and Hardwood Trees As the soil deepens even further broadleaf and hardwood trees take over. Hardwood forest in the final stage of succession in many areas.                       

Climax Community A community that does not undergo further succession. Climax communities are usually highly diverse and can often survive even severe local disturbances.

Primary Succession

Primary Succession Only occurs on freshly exposed rock or in places where a severe disturbance has occurred. However most disturbances are not this drastic.

Secondary Succession A fire may kill many plants but leave the soil in place. Living things can quickly colonize these types of areas. Define Secondary Succession. Examples: Storms, Fires and human activity

Deforestation

Secondary Succession Secondary succession resembles the later stages of primary succession. 1st to colonize are: Next to colonize: Final to colonize:

Secondary Succession Research has shown that many habitats never develop climax communities. Why? Example

Secondary Succession

Aquatic Succession Newly formed mountain lake. Low nutrient levels Supports few organisms. Reeds and other aquatic plants. Organic matter builds up and lake fills with sediment. Nutrient rich water Increase in wildlife Water plants cover the surface. Lake fills with sediment Marsh Land plants begin to colonize Finally Fertile Meadow (possibly a forest)

Island Succession Similar to succession on the continents. Any organisms found on an island must have ancestors that were: Carried by water Carried by wind Carried by other organisms Many islands have large bird populations.

Island Succession There are many unfilled niches on islands. Organisms can evolve to fit many niches. When a population of organisms adapted to their new niches new species are formed. Example: Figure 6.9 p. 95

Review How does primary and secondary succession differ from each other? What is a climax community? What is a pioneer community? Describe the sequence of ecological succession in a lake and on an island.

6.3 Stability in the Ecosystem

Objectives Explain the concept of ecosystem stability. Characterize the effects of disturbances on the ecosystem

Stability is a measure… …of how easily an ecosystem is affected by a disturbance. …how quickly it returns to its original condition after a disturbance. Conditions include: biotic and abiotic factors, patterns of energy flow and nutrient cycling.

More stable ecosystem Will return steady pattern of energy flow Experience fewer food web changes. Fewer evolutionary changes Fewer changes in the abiotic environment.

Stability in the Ecosystem Determined by the complexity of food web Manages the system’s energy flow and nutrient cycles. More connections=stability Impact of disturbance is less.

Equilibrium State of balance Changes counteract other changes. Weather cooling is counteracted by the evolutionary adaptation to cold weather. Disturbed ecosystem returns to a state of equilibrium (balance).

Ecosystem Function Scientist do not understand every detail of how even simple ecosystems function. They do understand that a change in one part of triggers a change in another. Scientists are trying to apply the chaos theory.

Chaos Theory A type of mathematics Suggests that ecosystem may be sensitive to even small changes The beginning state of an ecosystem is crucial to its later development.

Species Extinction Species are becoming extinct at an alarming rate. Fastest since the extinction of dinosaurs. Possible causes: Human Growth Habitat destruction Introduction of foreign species Pollution of fresh water

Thought It is difficult for scientists to predict the long-term effects of humans on the biosphere. And for them to predict the ability of the biosphere to support human population.

Review What makes an ecosystem stable? What happens to a stable ecosystem when a disturbance occurs? What happens to a ecosystem that is unstable when a disturbance occurs?

6.4 Land Biomes

Objectives Explain the concept of the biome, and name the eight major land biomes. Name an area in which each type is located.

Biomes Earth is very large and diverse Environments range from the ice of Antarctica to the heat and rain of the Amazon. Difference in temperature and rainfall create a vast array of conditions. Life has adapted to almost all of these conditions.

Biomes Definition-major type of ecosystem with distinctive temperature, rainfall and organisms. Either terrestrial or aquatic.

Biomes Biome is the largest general category used to classify ecosystems Conditions may vary from place to place Smaller ecosystems within a biome may have different habitats with different conditions and organisms. Every habitat on Earth is different. Term Biome is useful when discussion related habitats.

Aquatic Biomes Determined by: Water depth Nutrients Nearness to land

Terrestrial Biomes Determined by: Average temperature Amount of precipitation 8 major types of land biomes Desert Tundra Coniferous forest Deciduous forest Rain forest Steppe Prairie Savanna

Desert Low humidity High summer temperatures Low annual rainfall Supports only a small amount of biomass Deserts cover 25% of Earth’s land surface Deserts contain only 1% of Earth’s biomass Plant life is scarce in a desert due to lack of water

Desert in Australia

Tundra Cold Windy Dry South of polar ice caps in Alaska, Canada, Greenland, Iceland, Norway and Asia Very little plant life due to lack of water

Tundra

Forest Biomes Contains 75% of Earth’s Biomass Three types: Coniferous forest- containing conifers. Deciduous forest – containing deciduous trees. Rain forest –dense canopy of evergreen, broadleaf trees that receives at least 200 cm of rain each year.

Deciduous Forest

Coniferous Forest - Yosimite

Amazon Rain Forest

Rain forest Covers only 6% of Earth’s land surface. Contains more than 50% of all Earth’s biomass. Most diverse biome. Destruction of the rain forest is a HUGE environmental problem

Grasslands Cover 22% of Earth’s land surface Contain 8% of Earth’s biomass. Grasslands receive less precipitation than do forests and may have long dry seasons. May experience frequent fires Home to large herds of migrating herbivores Three types: Steppe Prairie Savanna

Steppe Grassland Biome Receives less than 50cm of rain per year Characterized by short bunchgrasses.

Steppe

Prairie Grassland Biome Characterized by: Rolling hills Plains Sod-forming grasses

Prairie

Savanna Grassland Biome Tropical Ranging from dry scrubland to wet, open woodland

Savanna - Africa

Review What is a biome? What are the 8 major types of land biomes? What type of land biome covers the largest land area? What type of land biome contains the most biomass?