Chapter 6 notes

Chapter 6 Ecosystem Balance: 

Chapter 6 Ecosystem Balance All the organisms in an ecosystem work together to capture energy and cycle matter This is to maintain balance and keep the ecosystem functioning Changes in the ecosystem is going to happen, no matter how stable the ecosystem is. Most changes are gradual, but some are severe (fires, storms, earthquakes) and cause rapid changes The ecosystem has to adapt to these changes to keep the flow of energy and matter going

Relationships in the ecosystem: 

Relationships in the ecosystem Species have several types of relationships with each other and their environment Predators & Prey Relationship Consumers that actively hunt other living organisms are predators. The organism a predator eats is the prey. Predators are often prey to other predators higher in the food chain. The population size b/n predator & prey are closely related If there is a big prey population available, a predator population will be large also If the prey population shrinks, the predator population will shrink also Ex: snowshoe hare and lynx Fig 6.1, pg 89 If the number of hares declines, the number of lynxes declines after about 1-2 years

Slide3: 

The lynx and hare populations rise and fall about once every 10 years, called its population cycle Population cycle is the amount of time between the rise and fall of a species population Large herbivores (hare, muskrat, large birds) have pop. cycles of about 10 years Small herbivores (mice, lemmings) have pop. cycles of about 4 years Why? Larger animals have longer cycles b/c they live longer and reproduce more slowly than smaller animals Predators often have pop. cycles that are the same as their prey because they depend on the prey to live. Ex: arctic fox eats herbivores with a 4 year cycle, so the arctic fox has a 4 year cycle

Parasitism Relationship: 

Parasitism Relationship Parasitism-a relationship in which one organism feeds on the tissues or body fluids of another organism the parasite does not kill the organism first The organism the parasite feeds on is the host it lives on or in the body of the host It often ends up killing or harming the host Ex: fleas, ticks, lice, some worms, protists It depends on the host for food, and many other functions Ex: tapeworms cannot move and have no sense organs (sight, touch, smell) The tapeworm lives in intestines of mammals. It doesn’t have to move or use any senses because the host does everything for it

Slide5: 

Population size of the parasite is close to the population of its host They are also density dependent on the population of the host. If the host population is crowded and live closely, then the parasite can be transferred easily to new hosts. Parasites are a density-dependent limiting factor. Symbiosis Relationship Any relationship in which two species live closely together is called symbiosis Parasitism is type of symbiosis, in which one organism harms another Symbiosis can either: Harm one organism, benefit the other (parasitism) Benefit one organism, do nothing to the other Benefit both organisms

Slide6: 

When one organism benefits, and the other is left alone, this is called commensalism Ex: barnacles live on the skin of whales without harming or helping the whale Barnacles benefit because the water passes over the whale giving it food When both species benefit this is called mutualism. Ex: stinging ants and the acacia tree Ex: flowers and insects The flower gives the insect food (nectar) The insect pollinates the flower by bringing pollen from another flower Ex: yucca plant and yucca moth are so mutualistic that they can’t survive without each other The moth lays its eggs inside the flower. It also gets food from the plant for its caterpillars. The flower is pollinated by the moth. The moth gets pollen from another yucca plant and brings it to its partner plant

Ecological Succession: 

Ecological Succession Environments will change causing old niches to have to change All the living things have to evolve to the changing environment of the ecosystem Brand new environments do become available to living things When volcanic eruptions, glaciers moving & other natural occurrences happen, they can wipe out a complete current ecosystem, including the soil It is left with nothing but bare rock or cooled lava. No living things are present and no soil Organisms will begin to move immediately into this brand new lifeless habitat The order of the organisms moving in usually follows a specific pattern =primary succession 1st thing to happen is colonization of new organisms and formation of new soil from rocks Rocks are broken down by lichen (a fungus/alga that releases acid) and weathering to form soil Lichen=pioneer community b/c 1st to colonize

Slide8: 

2nd, once there is soil, grass and small plants grow More soil is made from roots and dead leaves Lichen will be replaced by grass 3rd, After many generations, the soil is deep enough and fertile for nonwoody plants with deep roots At this point, small disturbances can cause drastic changes because the habitat is not stable yet 4th,Eventually, pine trees and others with shallow roots will grow when the soil is deep enough 5th Lastly, broadleaf trees and hardwood trees grow and replace many of the other pines This is the final stage of succession in most areas This ecosystem will probably not change much as long as there are no major disturbances It is called a climax community =a community that does not undergo further succession Climax communities usually are very diverse, have many different species, and can survive most severe disturbances

Slide9: 

Primary succession occurs on bare rocks or areas where there are no organisms or soil Many times, a disturbance doesn’t completely wipeout a habitat and its soil (fires, storms, human activity) When organisms begin to recolonize these areas it is called secondary succession= succession that occurs where a disturbance eliminates most organisms but does not destroy the soil Secondary succession happens in the order of the later stages of primary succession. 1st fast growing grass and nonwoody plants grow and then shrubs 2nd fast growing trees like pines grow 3rd slow growing hardwood trees grow Then a climax community forms This can take several hundred years to reach If major disturbances occur too often, climax communities may never be reached Grasslands have difficulty reaching a climax community because frequent fires disrupt and kill trees and shrubs They get stuck at the grass-community level

Aquatic Succession: 

Aquatic Succession Succession also occurs in aquatic habitats Ex: a glacier retreats and forms a clear mountain lake It has no organisms living in it and few nutrients What is going to move in first, second, third??? 1st small water plants, reeds will grow in the thin soil near the shore This supplies some organic matter for other small organisms 2nd, the water will gain more sediment, soil, and nutrients More organisms are supported, and water plants cover the surface of the lake 3rd, lake will fill with sediment and form a marsh Land plants will colonize It could eventually become a meadow covered with land plants and then grow into a forest

Island Succession: 

Island Succession Succession also occurs on islands just like on land New islands are formed by volcanic eruptions Organisms are quick to colonize on islands (seagulls) Any organism that colonizes on an island must have been carried by water, wind, or another organism Islands usually have large bird populations b/c birds can travel long distances easier than land animals New islands have many unfilled niches available to the organism that can reach the island The organism that would normally fill the niche, probably can’t get there This allows a species to evolve into many niches b/c there’s no competition Often results in new species (ex: Galapagos finch)

Maintaining Stability in the Ecosystem: 

Maintaining Stability in the Ecosystem Stability is the measure of how easily an ecosystem is affected by a disturbance and how quickly it goes back to its original condition after the disturbance The original condition of the ecosystem includes the biotic and abiotic factors, energy flow and nutrient cycle A more balanced ecosystem will be able to return to its original condition quicker and with fewer evolutionary changes in its organisms after a major disturbances A more complex food web increases the stability of an ecosystem All ecosystems are trying to maintain a state of balance, called equilibrium After a major disruption, ecosystems have to change drastically to adjust to the new conditions Sometimes the disruption can destroy an entire ecosystem A new ecosystem will eventually develop

Slide13: 

Dinosaurs were wiped out by a major disturbance (by a comet or climate changes) After that ecosystem was destroyed, many mammals evolved to the new ecosystem giving us many of the mammals we know of today It is impossible for scientists to predict how every change will affect an ecosystem There are too many abiotic and biotic factors which make the ecosystem too complex to predict Species are becoming extinct at a very high rate presently Human population growth is a major cause of this extinction rate Humans destroy habitats, introduce foreign species to new ecosystems, and pollute land, water and air

Land Biomes: 

Land Biomes The ecosystems of Earth can be divided into major categories Biome-a major type of ecosystem with distinctive temperature, rainfall and organisms Land biomes depend on average temp and amount of precipitation Aquatic biomes depend on water depth, nutrients, and nearness to land Biomes are broad, general categories that will vary within each individual biome Biomes include ecosystems which include habitats The habitats and ecosystems within a biome will be different, but overall fit within a biome category 8 Land biomes: desert, tundra, coniferous forest, deciduous forest, rain forest, steppe, praire, savanna Desert and tundra receive little water, support little biomass Forest biomes are 75% of Earth’s biomass Rain forest has more than 50% biomass Rain forest is the most diverse biome, it has the highest number of different species Rain forest destruction is very serious

Slide15: 

Grasslands contain about 8% of Earth’s biomass, but receive less precipitation than forest biomes. They have long dry seasons and have frequent fires Use the Biome map on pg 100-101