ECOLOGY REVIEW

Dr. Edelberg

What is ecology?

• Ecology is the study of interactions between living things and between living and non living things

What are abiotic factors?

• Abiotic factors include all the non living things that living things interact with

• For example the sun provides energy, carbon dioxide and water are needed for photosynthesis. Oxygen is required for cell respiration.

• Sun, water, carbon dioxide, oxygen are all abiotic factors.

What are biotic factors?

• Biotic factors include all the living things and once living things.

What are the levels of Ecological organization?

• Populations-A group of organisms of the same species that can mate, produce fertile offspring, and live in same location.

• Community-A group of interacting populations living in the same area (includes only biotic factors).

• Ecosystems-Community (all the living) plus all abiotic factors in a particular location.

Energy flow in an ecosystem

• All organisms require energy• Solar energy provides practically all the energy

for ecosystems.• Living things in an ecosystem can be classified

according to how they obtain energy-autotrophs or heterotrophs.

• Autotrophs convert energy from the sun into chemical energy stored in the bonds of organic molecules (photosynthesis).

Energy Flow continued• Heterotrophs can’t produce their own food directly from

sunlight and inorganic compounds. They require energy previously stored in organic molecules.

• Autotrophs are called primary producers• Heterotrophs can be grouped as consumers or decomposers• Consumers can be herbivores, carnivores, omnivores or

detritvores-invertebrates that feed on organic wastes and dead organisms.

• Energy flow is one directional moving from sun to producers to consumers to decomposers and eventually lost as heat (can’t be reused).

What is a food chain?

• A food chain is a simple model that shows how energy and nutrients move through an ecosystem.

• A food chain is composed of feeding levels called trophic levels

What are the trophic levels?

• First trophic level are the primary producers-make their own food

• Second trophic level are the primary consumers- obtain food by eating producers. They are considered herbivores because they eat only plants.

• Third trophic level- are the secondary consumers-obtain food by eating primary consumers. They are considered carnivores if they eat meat or omnivores if they eat meat and plants.

What are the trophic levels-continued

• Fourth trophic level-are the tertiary consumers-obtain their food by eating secondary consumers.

• Decomposers are considered a trophic level but have no number because they feed on other trophic levels. Break down dead material into inorganic material. Bacteria and fungi are the main decomposers.

Energy flow in an ecosystem

Foodchains

What is the amount of energy available at each trophic level?

• 90% of energy lost in each trophic level• Producers (1st trophic level) get 100% of energy

available.• Primary consumers (2nd trophic level) get 10% of

available energy.• Secondary consumers (3rd trophic level) get 1% of

available energy.• Tertiary consumers (4th trophic level) get 0.1% of

energy available.

Energy available continued

• Thus the amount of energy available limits the food chain to 4-5 links.

• The greatest amount of energy is in the first trophic level and the least amount of energy is in the higher trophic levels

• More efficient to feed at lower trophic levels

Ecological pyramids

• Ecological pyramids are models that show amounts at each trophic level and the change from level to level.

• Energy pyramids show the amount of energy at each trophic level.

• Biomass pyramids show the amount of biomass (dry weight of living tissue) at each trophic level

• Numbers pyramid shows the number of organisms at each trophic level.

Energy pyramid

• Shows that each higher trophic level must have less energy than lower levels due to loss of energy as heat (via cell respiration) at each level.

Numbers pyramid

• Numbers pyramid indicates the number of individuals in each trophic level.

• Sometimes get inverted numbers pyramid. For example one tree can support many consumers.

• Energy pyramids can never be inverted.

Biomass pyramid

• Pyramid of biomass shows amount of biomass at each trophic level. Can’t be inverted.

What is a food web?

• A group of interconnecting food chains.• Shows all the possible feeding relationships in

an ecosystem.• More realistic than a food chain since most

organisms feed on more than one thing.

FOOD WEB

Nutrients also move through ecosystems

• Nutrients move through ecosystems vias trophic levels

• Unlike energy, nutrients are recycled• Nutrient cycles include the water cycle, carbon

cycle, nitrogen cycle, and phosporus cycle

Water Cycle

• Evaporation• Transpiration-Leaf sweating• Condensation• Precipitation• Runoff

Carbon Cycle

• Atmospheric carbon dioxide (burning fossil fuels and cell respiration)

• Death and decay result in fossil fuel formation• Photosynthesis (remove carbon dioxide from

air and move carbon to glucose housed in living things).

Carbon Cycle

Nitrogen cycle

• Bacteria capture nitrogen and bring it into living things

• Different bacteria return nitrogen back to atmosphere.

Community ecology focuses on interactions between organisms

• Types of interactions include• Competition• Predator-prey• Symbiotic

Competition

• Increases between specie swhen resources are scarce

• Niche is the role in plays in an ecosystem (how does it meet its food need?, Shelter? How and where it survives? how and when it reproduces?)

• Habitat is location that it lives. Habitat is one small part of an organisms niche.

Competitive exclusion principle

• States that no two species can occupy the same niche at the same time.

• Possible outcomes include extinction of one species or resource partitioning-splitting up of niche

Predator-Prey Relationships

• A predator eats prey• Since no community can carry more organisms

than its food, water, and shelter can accommodate it must stay in balance.

• Ecosystems will fail if they do not stay in balance.• To stay in balance predators and prey develop

adaptations-any inherited behavior or structure that provides a survival advantage in a particular environment.

Predator-prey continued

• Predator adaptations include teeth, claws, fangs, poison, heat sensing organs, speed and agility

• Outcomes of predator-prey interactions include offset oscillations in the population sizes of the predator and prey-as the predator population increases the prey population decreases, as the prey population decreases the predator population decreases, as the predator population the prey population increases causing the predator population to increase.

Predator-prey continued

• Another outcome may be co-evolution of predator prey. Each acts as a selective pressure on the other for adaptations. Each adapts to changes in the other.

Symbiosis (living together)

• A close and permanent relationship between two organisms of different species

• Three types of symbiotic relationships-mutualism, commensalism, and parasitism

Mutualism

• AAAAA symbiotic symbiotic relationship where both species benefit e.g.

1.        Clown fish and sea anemone2.       Humans and pets3.       Ants & Peony flowers4. Lichens – algae and a fungus

MUTUALISM-a symbiotic relationship where both species benefit

Commensalism

• A symbiotic relationship in which one species benefits and the other is neither helped nor harmed.

Parasitism

• A symbiotic relationship where one organism benefits and the other is harmed.

Succession

Both the biotic or living and the abiotic or non- living components of an ecosystem change over time.

• Will this landscape of rocks remain this way forever?

The answer is, “NO!”

• Over the years, one kind of community is replaced by another kind of community until eventually, a stable community develops.

• The gradual change in a community is known as succession.

Two Types of Succession

• Primary Succession: The process of creating life in an area where no life or soil previously existed.

• Secondary Succession: The process of re-rebuilding a previously existing community after being destroyed by some disaster like fire. Soil exists.

Primary succession

• The development of an ecosystem in an area that has never had a community living within it occurs by a process called PRIMARY SUCCESSION.

• An example of an area in which a community has never lived before, would be a new lava or rock from a volcano that makes a new island.

Primary Succession

• Begins in a place without any soil – Sides of volcanoes– Receding Glaciers

• Starts with the arrival of living things such as lichens that do not need soil to survive.

• Called PIONEER SPECIES• Lichen is a classic Pioneer species

Pioneer Organisms

• Primary succession on land begins in an area where there are no living things and no soil.

• The first plants or plant-like organisms that arrive are called pioneer organisms.

• They can grow on bare rock without soil eventually breaking it up and helping soil to form. These include lichens and algae.

Modification of the environment• Soil starts to form as lichens and the forces of weather and

erosion help break down rocks into smaller pieces.• When lichens die, they decompose, adding small amounts of

organic matter to the rock to make soil

Creation of New Soil

• Creation of soil allows plants to grow.

Primary Succession

• Simple plants like mosses and ferns can grow in the new soil

Primary Succession

• The simple plants die, adding more organic material.

• The soil layer thickens, and grasses, wildflowers, and other plants begin to take over.

• Then These plants die, and they add more nutrients to the soil.

• Shrubs and tress can now survive now.

Primary Succession

• Insects, small birds, and mammals have begun to move in.

• What was once bare rock now supports a variety of life.

Pictures of Succession

• One sequence of plant succession in New Jersey might be lichens----then----grasses---shrubs----conifers (pine trees)----deciduous forests(beech and maple trees).

Climax Community

• Succession ends with the development of a climax community. Here, the plants and animals exist in balance with each other and the environment. For example, in New Jersey a hemlock-beech-maple forest is a climax community. Animals that reside here include, chipmunks, deer, bear, turkeys, rabbits, squirrels, fox, birds, to name a few!

Typical New Jersey State forest

Animals in a hemlock, beech, maple forest

Animals found in a TYPICAL New Jersey State forest

Climax communities are stable

• The climax community will exist indefinitely without further change, unless something catastrophic occurs. A volcanic eruption or a forest fire, will alter and possibly destroy the climax community. Then, ecological succession begins again and after many years, a new climax community will develop.

Secondary Succession

• Begins in a place that already has soil and was once the home of living organisms

• Occurs faster and has different pioneer species than primary succession

• Example: after forest fires

Secondary succession• SECONDARY SUCCESSION begins in habitats where communities were

entirely or partially destroyed by some kind of damaging event.

• When an existing community has been cleared by a disturbance such as a fire, tornado, etc...and the soil remains intact, the area begins to return to its natural community. Because these habitats previously supported life, secondary succession, unlike primary succession, begins on substrates that already bear soil. In addition, the soil contains a native seed bank.

• Since the soil is already in place, secondary succession can take place five to ten times faster than primary succession.

Why Does Ecological Succession Occur?

• Organisms alter their environment• Organisms become less suitable for

environment• New organisms better adapted to changes in

the environment come in and out compete original organisms

A Summary of Changes That occur During Succession

• Pioneer species colonize a bare or disturbed site. Soil building. • Changes in the physical environment occur (e.g., light, moisture).

• New species of plants displace existing plants because their seedlings are better able to become established in the changed environment.

• Newly arriving species alter the physical conditions, often in ways that

enable other species to become established. • Animals come in with or after the plants they need to survive. • Eventually a climax community that is more or less stable will become

established and have the ability to reproduce itself. • Disturbances will start the process of succession again.

Does Ecological Succession Ever Stop?

• No

• Do Humans Affect Ecological Succession?