What is Ecology?

• The branch of biology that developed from natural history is called ecology.

• Ecology is the study of interactions that take place between organisms and their environment.

• Ecologists may ask what a coyote eats, how day length influences plants or migrating birds, or why tiny shrimp help rid ocean fishes of parasites.

The Biosphere

• On earth, living things are found in the air, on land, and in both fresh and salt water.

• The biosphere is the portion of Earth that supports living things.

• Range of the biosphere is from high in the atmosphere to the bottom of the oceans.

• The biosphere supports a diverse group of organisms in a wide range of climates.

• The climate, soils, plants, and animals in one part of the world can be very different from those same factors in other parts of the world.

• Living things are affected by both the physical or nonliving environment and by other living things.

• Factors that affect organism are both abioticand biotic.

Abiotic Factors

• Examples of abiotic factors include air currents, temperature, moisture.

• Ecology includes the study of features of the environment that are not living because these features are part of an organism’s life.

• Abiotic factors have obvious effects on living things and often determine which species survive in a particular environment.

Biotic Factors

• Living things affect other living things.

• All organisms depend on others directly or indirectly for food, shelter, reproduction, or protection.

• Examples plants, animals, bacteria, any thing that is living.

Levels of Organization

• To help ecologists understand the interactions of biotic and abiotic parts of the world, they have organized the living world into levels.

• 1. Organism- an individual living thing that is made of cells, uses energy, reproduces, responds, grows and develops.

• 2. Population- A group of organisms, all of one species, which interbreed and live in the same place at the same time.

• 3. Biological community- all the populations of different species that live in the same place at the same time.

• 4. Ecosystem- populations of plants and animals that interact with each other in a given area and with the abiotic components of that area.

• 5. Biosphere- the portion of earth that supports life.

Interactions within populations

• Organisms in a population share the resources of their environment may determine how far apart the organisms live and how large the populations become.

• Compete with each other for food, water, mates, or other resources.

• Competition increases when resources are in short supply.

Interactions within communities

• A change in one population in a community may cause changes in the other populations.

• Changes can be minor like an increase in predators cause a decrease in prey.

• Changes can be major like a population may use up the resources and in turn affecting another population.

Biotic and abiotic factors form ecosystems

• Biotic factors like insects, grass, trees, squirrels and abiotic factors like water, temperature make an ecosystem.

• Two major kinds of ecosystems-terrestrial ecosystems (forest, meadows, etc.)and aquatic ecosystem (salt water and fresh water)

Organisms in ecosystems

• The place where an organism lives out it’s life is a habitat.

• Ecosystems covers a large area of the earth. Habitat covers a small area of an ecosystem.

• Habitat size varies from organism to organism.

• Habitats are also shared with different species of organism.

Survival Relationships• A predator is a type of consumer like a lion or

an insect-eating bird.

• The animals predators eat are called prey.

• Predator-prey relationships such as the one between cats and mice involve a fight for survival.

• But not organisms living in the same environment are in a continuous battle for survival.

• Studies have shown that most species survive because of the relationships they have with other species.

• The relationship in which there is a close and permanent association between organisms of different species is called symbiosis.

• Symbiosis means living together.

The three kinds of symbiotic relationships

• 1. Mutualism

• Two species of organisms benefit from living in close association.

• Ex. Ants and acacia trees living in the subtropical regions of world. The ants protect the acacia tree by attacking any animal that tries to feed on the tree. The tree provides nectar and a home for ants.

• 2. Commensalism

• One species benefits and the other species is neither harmed nor benefited.

• Ex. Spanish moss on the branches of trees. The moss benefits because it uses the tree for support. It holds on to the tree. The tree does not benefit but is not getting harmed either.

• 3. Parasitism

• One organism benefits while harming another.

• Ex. Ticks or fleas on animals. The ticks or fleas gets nutrients from animal.

• Parasites have evolved in such a way that they harm, but usually do not kill the host species.

• If host dies then parasite dies also if they don’t find another host.

• Other examples of parasites: certain bacteria, tapeworms, roundworms, mistletoe.

Nutrition and Energy Flow

Ecologists trace the flow of energy through communities to discover nutritional relationships between organisms.

The producers: Autotrophs

The ultimate source of the energy for life is the sun. Plants use the sun’s energy to manufacture food in a process called photosynthesis.

Grass and trees are autotrophs. Some unicellular organisms such as green algae, also make their own nutrients.

Other organisms in the biosphere depend on autotrophs for nutrients and energy. These dependent organisms are called consumers.

The consumers: HeterotrophsA bison eats grass, a deer nibbles the leaves of a clover plant and owl swallows a mouse.

The bison, deer and owl are consumers, incapable of producing their own food. They obtain nutrients by eating other organisms.

Heterotrophs include organisms that feed on only autotrophs, feed on only other heterotrophs, or feed on both autotrophs and heterotrophs.

Types of heterotrophs1. Herbivore – a heterotroph that feeds only on plants. Ex. Rabbits, grasshoppers, squirrels, bees.

2. Heterotrophs that eat other heterotrophs.

1.Carnivores- animals that kill and eat only other animals. Ex. Lions,

2. Scavenger- do not kill for food but eat animals that have already died. Ex. Black vultures.

3. Omnivores- consume both autotrophs and heterotrophs (plants and meat). Ex. Raccons, opossums and bears.

Decomposers – organisms that break down dead and decaying plants and animals into simpler molecules that can be more easily absorbed. Ex. protazoans, many bacteria, and most fungi.

Flow of matter and energy in ecosystems

When you eat food, such as an apple you consume matter.

Matter, in the form of carbon, nitrogen, and other elements, flow through the levels of an ecosystem from producers to consumers.

The apple also contains energy from sunlight that was trapped in the plant during the process of photosynthesis .

As you cycle the matter of the apple, some trapped energy is transferred from one level to the next. At each level, a certain amount of energy is also transferred to the environment as heat.

Question

How do matter and energy flow through ecosystems?

Food chains: Pathways for matter and energy

A food chain is a simple model that scientist use to show how matter and energy move through an ecosystem.

In a food chain, nutrients and energy move from autotrophs to heterotrophs and, eventually, to decomposers.

A food chain is drawn using arrows to indicate the direction in which energy is transferred from one organism to the next.

Ex. Berries mice black bear

Most food chains consist of two, three, four transfers. The amount of energy remaining in the final transfer is only a portion of what was available at the first transfer. A portion of the energy is given off as heat at each transfer.

Trophic levels represent links in the chain

Each organism in a food chain represents a feeding step, or trophic level, in the passage of energy and materials.

A first order heterotroph is an organism that feeds on plants, such as a grasshopper.

A second order heterotroph is an organism that feeds on the first order heterotroph. Ex. Bird that feeds on a grasshopper.

A food chain represents only one possible route for the transfer of matter and energy through and ecosystem.

Many other routes may exist. Many different kinds of organisms eat a variety of foods, so a single species may feed at several trophic levels

The Food Web

Ecologists interested in energy flow in an ecosystem may set up experiments with as many organisms in the community as they can.

Food web shows all the possible feeding relationships at each trophic level in a community.

Food web represents a network of interconnected food chains formed by herbivores and carnivores.

Energy and trophic levels: Ecological Pyramids

• An ecological pyramid can show how energy flows through an ecosystem.

• The base of the ecological pyramid represents the autotrophs, or first trophic level.

• Higher trophic levels are layered on top of one another

The pyramid of energy illustrates that the amount of available energy decreases at each succeeding trophic level.

The total energy transfer from one trophic level to the next is only about ten percent because organisms fail to capture and eat all the food energy available at eh trophic level below them.

Cycles In NatureSince energy is also transferred to the environment as heat generated by the body processes of organisms.

Sunlight is the primary source of all this energy, and is always being replenished by the sun.

Matter, in the form of nutrients, also moves through, or is part of, all organisms at each trophic level. But matter is cycled and is not replenished like the energy from sunlight.

• There is a finite amount of matter.

The atoms of carbon, nitrogen, and other elements that make up the bodies of organisms alive today are the same atoms that have been on Earth since life began.

Matter is constantly recycled. It is never lost.

The water cycleLife on earth depends on water.

1. Evaporation- water evaporates from lakes and oceans and becomes water vapor in the air.

2. Transpiration- the loss of water through the leaves of plants.

Where do the drops of water that form on a cold can of soda come from?

The water vapor in the air condenses on the surface of the can because the can is colder than the surrounding air.

3. Condensation- water vapor condenses. Forms clouds.

4. Precipitation- rain, ice, or snow

Animals breathe out water vapor when they breath. When they perspire or urinate, water also is returned to the environment.

The carbon cycle

All life on Earth is based on carbon molecules.

Atoms of carbon form the framework for proteins, carbohydrates, fats, and other important molecules.

Carbon is the molecule of life.

During photosynthesis, energy from the sun is used by autotrophic organisms to convert carbon dioxide gas into energy-rich carbon molecules that many organisms use for food and a source of energy.

Plants take in carbon in the form of carbon dioxide for growth and energy.

Heterotrophs, which feed either directly or indirectly on the autotrophs, use these carbon molecules for growth and energy.

Carbon is taken out of the atmosphere by photosynthesis.

Carbon is put back in the atmosphere by respiration, fuel combustion, and open burning

The nitrogen cycle

When you add nitrogen fertilizer to a lawn, houseplants, or garden, you may see that they become greener, bushier, and taller.

Even though the air is 78% nitrogen, plants seem to do better when they receive nitrogen fertilizer.

This is because most plants cannot use the nitrogen in the air. They use nitrogen in the soil that has been converted into more usable forms.

Certain bacteria convert the nitrogen from air into these more usable forms. Chemical fertilizers also give plants nitrogen in a form they can use.

The cycle:

1. Nitrogen fixing bacteria convert nitrogen in a form that plants can use.

2.Plants use nitrogen to make molecules such protein.

3. Herbivores eat plants and convert plant’s protein into an animal protein.

4. Then carnivores eat herbivores and convert the protein in a form that they require.

5. Urine, contains nitrogen compounds so animal put nitrogen back to the water or soil.

6. Organism die and decay, nitrogen returns to the soil and eventually to the atmosphere or plants can reuse the nitrogen.

7. Soil bacteria also act on these molecules and put nitrogen back into the air.

The Phosphorus Cycle

All organisms require phosphorus for growth and development. Phosphorus cycles in two ways.

Short term cycle.

1. Plants obtain Phosphorus from the soil.

2. Animals obtain phosphorus by eating plants.

3. When animals die, they decompose and the phosphorus is returned to the soil to be used again.

Long term cycle

Phosphates washed into water become incorporated into rock as insoluble compounds. Millions of years later, as the environment changes, the rock containing phosphorus is exposed. As the rock erodes, the phosphorus again becomes part of the local ecological system.