Biology 20: Chapter 4 — Characteristics of Ecosystems

125 flashcards covering the Chapter 4 PowerPoint and all Brightspace learning outcomes.

What is ecology?

The study of how organisms interact with one another and with their environment.

What is an abiotic factor? Give examples.

A non-living environmental factor, such as sunlight, temperature, water, soil, oxygen, salinity, or pressure.

What is a biotic factor? Give examples.

A factor caused by living organisms and their roles, such as predators, prey, competitors, parasites, decomposers, or food availability.

What is an ecosystem?

A community of living organisms together with the physical, chemical, and non-living environment with which they interact.

Why do ecosystems not have perfectly sharp boundaries?

Organisms and materials move between ecosystems, and neighbouring ecosystems often blend through a transition area.

What is an ecotone?

A transition area where two ecosystems meet and species from both ecosystems interact.

Why do ecotones often have high biodiversity?

They contain species from both neighbouring ecosystems and sometimes species specialized for the transition zone.

Why can greater biodiversity make an ecosystem less fragile?

More species provide alternative food sources and ecological roles, so the loss or decline of one species is less likely to collapse the whole system.

How does a natural ecosystem differ from an artificial ecosystem?

A natural ecosystem is not planned or maintained by humans; an artificial ecosystem is created, planned, or maintained by humans and usually has a simpler food web.

What is an ecological niche?

An organism's complete role in an ecosystem, including its habitat, place in the food web, breeding area, time of activity, resource use, and everything it does to survive and reproduce.

How is a niche different from a habitat?

A habitat is where an organism lives; a niche is how it lives and functions there.

Why do closely related species often have slightly different niches?

Niche differences reduce direct competition for the same territory, food, time, and other resources.

What can happen when two species occupy very similar niches?

Strong competition occurs. One may outcompete the other, the species may divide resources, or one may move or adapt to a different niche.

How do owl and hawk niches reduce competition?

Owls usually hunt at night in forests and nest deep in trees; hawks generally hunt by day over fields or grasslands and nest near treetops.

Why can an ecosystem with many niches support more organisms?

More distinct roles and resource-use patterns allow more species to coexist with less direct competition.

Why can introducing an exotic species cause depletion or extinction?

The new species may lack natural predators or controls, outcompete native species, or prey on organisms that have no effective defence.

What introduced plant is used as an example in the presentation?

Purple loosestrife, an exotic weed that is difficult to control in Canada.

What is a population?

All members of the same species living in a particular ecosystem or area.

What is a community?

All the populations of different species that live and interact in an ecosystem.

What is a habitat?

The physical place where an organism lives and obtains the conditions and resources it needs.

Put these levels in order from narrowest to broadest: ecosystem, organism, community, population.

Organism -> population -> community -> ecosystem.

What does an ecosystem contain that a community does not?

The abiotic environment. A community includes only living populations; an ecosystem includes the community plus non-living surroundings.

What is a biome?

A large geographic region with a characteristic climate and organisms adapted to that climate, often identified by a dominant type of vegetation.

What two climate variables are especially important in determining biomes?

Average temperature and precipitation.

What are Alberta's four major terrestrial ecosystem types in this chapter?

Taiga, muskeg, grassland, and deciduous forest.

What are key abiotic features of Alberta taiga ecosystems?

North/central Alberta forests, changeable weather, acidic soil containing some water, and roughly 50-250 cm of precipitation per year.

What organisms are typical of the taiga ecosystem?

Black and grizzly bears, wolverines, weasels, moose, deer, grouse, owls, spruce and pine trees, shrubs, ferns, mosses, and lichens.

What are key abiotic features of muskeg ecosystems?

Cold temperatures, a short growing season, permafrost beneath the surface, and relatively low precipitation of about 25-100 cm per year.

What organisms are typical of muskeg ecosystems?

Black bears, caribou, ptarmigan, rapidly flowering plants, mosses, and lichens.

What are key abiotic features of Alberta grasslands?

South/central Alberta, more sunlight and warmth than muskeg or taiga, rich fertile soil, and about 25-100 cm of precipitation per year.

What organisms are typical of grassland ecosystems?

Bison, deer, rabbits, hawks, yellow-bellied sapsuckers, fescue grasses, and grasshoppers.

What are key abiotic features of Alberta deciduous forests?

Central Alberta, more sunlight and warmth than muskeg or taiga, rich fertile soil, and about 75-250 cm of precipitation per year.

What organisms are typical of deciduous forest ecosystems?

Black bears, weasels, moose, deer, woodpeckers, deciduous trees, and shrubs.

What is Alberta's major type of aquatic ecosystem?

Freshwater ecosystems, including lakes, ponds, and rivers.

What basic facts about Earth's water are emphasized in the chapter?

Water covers more than two-thirds of Earth, about 97% is salt water, and most freshwater is stored as snow and ice.

Why are oceans important even to freshwater ecosystems?

Oceans strongly influence weather and supply freshwater through evaporation and the water cycle.

What are the three main zones of a lake?

Littoral, limnetic, and profundal zones.

What is the littoral zone?

The near-shore area extending to the depth where rooted plants can no longer grow. It is usually the lake's most productive zone.

Why is the littoral zone highly productive?

Sunlight reaches the bottom, allowing rooted plants and algae to photosynthesize and support diverse food webs.

What is the limnetic zone?

The open-water region where enough light penetrates for photosynthesis; plankton are common there.

What is plankton?

Organisms that drift and cannot swim effectively against a current.

How do autotrophic and heterotrophic plankton differ?

Autotrophic plankton are tiny photosynthetic plants or algae; heterotrophic plankton are consumers, often small invertebrate animals.

What is the profundal zone?

The deep region below the limnetic zone where too little light penetrates for photosynthesis.

Why are few fish found in the profundal zone?

Decomposers use oxygen while breaking down sinking detritus, and no photosynthesis occurs there to replace the oxygen.

What chemical factors affect aquatic ecosystems?

Fresh versus salt water, dissolved oxygen, and dissolved substances such as nitrogen, phosphorus, minerals, and organic pollutants.

How do depth, light, and temperature affect aquatic life?

Light and temperature generally decrease with depth, so photosynthetic organisms remain near the surface while deep-water organisms face cold, darkness, and higher pressure.

How does water pressure change with depth?

Pressure rises by about 100 kPa for every 10 m of depth; at 10 m it is roughly twice surface pressure.

Why is deep-water pressure a limiting factor?

Few organisms have adaptations that let them function under the extreme pressure found at great depths.

Why can food webs exist around deep-ocean hydrothermal vents without sunlight?

Chemosynthetic bacteria make organic food using chemical energy and form the base of the food web.

Why does ice float, and why does deep lake water often remain near 4 degrees C?

Water becomes denser as it cools to 4 degrees C, then becomes less dense below 4 degrees C. Ice is less dense than liquid water, so it floats while denser 4 degrees C water sinks.

What happens to a lake in winter?

Ice and snow insulate the lake but reduce atmospheric oxygen entry. Water forms density layers, and thick snow or ice may block photosynthesis and lower dissolved oxygen.

What is spring turnover?

As surface water warms to 4 degrees C, it becomes dense and sinks. Wind mixes the lake and carries newly dissolved oxygen into deeper water.

What are the epilimnion, thermocline, and hypolimnion?

In summer, the epilimnion is the warm upper layer, the thermocline is the narrow layer of rapid temperature decrease, and the hypolimnion is the cold deep layer.

Why can both deep and shallow-water organisms face oxygen stress in summer?

Deep water receives little new oxygen after stratification, while warm surface water holds less dissolved oxygen and may lose too much during a hot spell.

What is fall turnover?

Cooling surface water reaches 4 degrees C and sinks, mixing the lake and renewing dissolved oxygen in deeper layers.

What are the four soil layers presented in the chapter, from top to bottom?

Litter, topsoil, subsoil, and bedrock.

What is the litter layer, and what does it do?

Partly decomposed leaves or grasses that act like a blanket, reducing temperature changes and water loss by evaporation.

What is topsoil?

Small rock particles mixed with humus. It contains minerals, nutrients, air, and water and supports most plant growth and decomposition.

What is humus?

Decaying plant and animal matter in soil that adds nutrients and improves soil quality.

What is subsoil?

A deeper layer with more rock and less organic matter than topsoil, often containing minerals such as iron, aluminum, and phosphorus.

What is bedrock?

The solid rock layer beneath the soil.

How does soil influence the biotic community?

Soil texture, nutrients, water, and pH determine which plants grow, which then influences the animals and other organisms the ecosystem can support.

What factors can affect soil pH?

Parent rock, the plants growing there, acids released during decomposition, and the acidity of rain, snow, and groundwater.

What is groundwater?

Water that has seeped into soil and porous rock below Earth's surface.

What is the water table?

The boundary between saturated ground below and unsaturated soil above.

What is leaching, and why can it be a problem for plants?

Downward-moving water dissolves and carries minerals and organic matter deeper, moving nutrients beyond the reach of many roots.

How does temperature affect terrestrial ecosystems?

It changes evaporation, growing-season length, metabolism, and survival, leading to adaptations such as evergreen needles, underground grass roots, migration, hibernation, overwintering eggs, and burrowing.

How does sunlight vary across and within ecosystems?

Day length varies with latitude and season. Within one ecosystem, tall plants create shaded microenvironments that favour shade-tolerant species.

What is biotic potential?

The maximum number of offspring a species could produce if resources were unlimited.

What four factors regulate biotic potential?

Birth potential, capacity for survival, breeding frequency, and length of reproductive life.

What is birth potential?

The maximum number of offspring produced per birth or reproductive event.

What is capacity for survival?

The proportion or number of offspring that survive to reproductive age.

What is breeding frequency?

The number of times a species reproduces in a given period, commonly per year.

What does length of reproductive life include?

The age when sexual maturity begins and the number of years during which an individual can reproduce.

What examples illustrate the four biotic-potential factors?

Whooping cranes illustrate low birth potential; sea turtles illustrate low survival to maturity; elk illustrate annual breeding frequency; elephants illustrate late maturity but a long reproductive life.

What is a limiting factor?

Any environmental factor or resource shortage that prevents a population from reaching its biotic potential.

What is carrying capacity?

The maximum number of individuals of a species that an ecosystem can support over time with its available resources.

Can a population exceed carrying capacity?

Yes, briefly. The resulting resource shortage raises mortality or lowers reproduction, pushing the population back toward a sustainable level.

Why do populations fluctuate around carrying capacity?

Biotic and abiotic limiting factors change over time, altering food, water, habitat, predation, disease, and survival.

What is the law of the minimum?

Growth is limited by the essential nutrient or resource in shortest supply, even when all other requirements are abundant.

What is the law of tolerance?

An organism can survive only within a certain range of an abiotic factor. Conditions above or below that range prevent survival or reproduction.

What parts appear on a tolerance curve?

An optimum range with the largest population, zones of physiological stress with fewer organisms, and zones of intolerance beyond the lower and upper limits where the species cannot survive.

What is a density-independent factor?

A factor that affects population members regardless of how crowded the population is.

What are examples of density-independent factors?

Flood, fire, drought, climate or temperature changes, pesticide spraying, and habitat destruction.

What is a density-dependent factor?

A factor whose effect becomes stronger as population density rises, often increasing mortality or reducing reproduction.

What are examples of density-dependent factors?

Food or water shortage, competition for mates or breeding areas, disease, parasites, increased predation, and sometimes effects of introduced species.

Why do diseases usually spread more easily in dense populations?

Individuals have more frequent contact and pathogens move between hosts more efficiently.

What is deforestation?

The removal of forest vegetation, which changes habitat, biodiversity, soil, water flow, and nutrient cycles.

What is slash-and-burn clearing?

Vegetation is removed, piled, and burned. Ash briefly adds nutrients, but repeated or large-scale use can destroy habitat and degrade soil.

What is clear-cutting?

Removing all trees from an area for timber or pulp, often followed by replanting one dominant species.

Why can clear-cutting be ecologically harmful?

It removes habitat at once, reduces biodiversity, increases erosion and runoff, and replacement with one species creates a simpler ecosystem.

What is selective cutting?

Harvesting only selected trees while leaving others to maintain habitat and regenerate the forest.

Which forestry practices are generally more sustainable, and why?

Carefully managed selective cutting, mixed-species regeneration, long harvest rotations, and protection of soil and waterways are more sustainable because they retain ecosystem structure and allow recovery.

Why is fire sometimes beneficial in an ecosystem?

Natural fire can recycle nutrients and create a mosaic of vegetation types and ages, increasing habitat variety.

What is a prescribed burn?

A carefully planned and controlled fire set in a designated area, monitored by trained workers and extinguished after its objective is reached.

What is an oligotrophic lake?

A typically deep, cold, nutrient-poor lake with low producer growth, relatively few organisms, and clear water.

What is a eutrophic lake?

A generally shallow, warmer, nutrient-rich lake with many producers and often murky water.

What is eutrophication?

The gradual nutrient enrichment and biological filling-in of a lake, eventually making it shallower and potentially converting it to dry land.

How can humans accelerate eutrophication?

By adding nitrogen, phosphorus, sewage, fertilizer runoff, household or industrial waste, and other nutrient-rich materials.

Why can nutrient enrichment eventually reduce dissolved oxygen?

Extra nutrients cause heavy plant and algal growth; when this biomass dies, decomposers consume large amounts of oxygen.