UNIT 2

THE ECOSYSTEM

2.1 BIOTIC, ABIOTIC FACTORS, AND TROPHIC LEVELS

BIOTIC FACTORS

• Biotic factors are the living components that shape an ecosystem; any organism that affects another organism.

• Biotic components are:

– Animals

– Plants

– Bacteria

– Fungi

ABIOTIC FACTORS

• Abiotic factors are the non-living components of an ecosystem, affecting the life of organisms.

• Abiotic factors can be harmful to the ecosystem.

• Abiotic components are:

– Temperature, light, water, soil, rocks, and human influence.

WATER

Water is one of nature’s most important things is life. Essential to life, an

organism’s survival depends an water. Water is necessary for digestion and absorption of food; helps maintain proper muscle

tone-, supplies oxygen and nutrients to the cells; rids

the body of water; and serves as a natural air conditioning system.

SUNLIGHT

The sun provides light and warmth and it is the energy source for almost all ecosystems

on Earth. Sunlight powers

photosynthesis by plants, the main producer in most

terrestrial ecosystems.

TEMPERATURE

Most life exists within a fairly narrow range of

temperatures, from about 0 C to about 50 C. Few

organisms can maintain an active metabolism below 0

C for long, and most organisms’ enzymes are

denatured (they lose their shape and stop working)

above 50 C. However, extraordinary adaptations enable certain species to

live at extreme temperatures.

SOIL

Soil is the product of abiotic forces (such as ice, rain, and

wind) and the actions of living things (such as

microorganisms, plants, and earthworms) on the rocks and minerals of Earth’s crust. The

structure and chemical makeup of soil and rock in an area affect the types of plants

that grow there. In aquatic environments as well, the

characteristics of underlying sand and rock affect the type of plants and algae that can grow. This in turn affect the

other organisms found there.

OXYGEN

Oxygen is an important component

of life. Most living things consume

oxygen in different forms and quantities. Most of the oxygen

that is used in respiration is to obtain chemical energy from

the fats and carbohydrates in our

food.

WIND

Many plants use the help of the wind to

disperse seeds over long distances.

Organisms disperse to find new habitats rich in needed resources. Strong winds can be

very destructive.

TROPHIC LEVELS

• There are trophic levels within an ecosystem; these are the feeding positions that biotic components occupy on the food chain.

• The word trophic derives from the Greek trophe referring to food or feeding.

• A food chain represents a succession of organisms that eat another organism and are, in turn, eaten themselves.

TROPHIC LEVELS

• Trophic levels in a food chain are:– Trophic level 1 – primary producers– Trophic level 2 – herbivores or primary consumers– Trophic level 3 – predators, carnivores which eat

herbivores or secondary consumers– Trophic level 4 – carnivores which eat other carnivores or

tertiary consumers– Trophic level 5 - apex predators which have no predators,

at the top of the food chain

The path along the chain forms a one-way flow along which energy travels in the form of food.

TROPHIC LEVELS

1. Producers - (autotrophs) are typically plants or algae. Plants and algae do not usually eat other organisms, but pull nutrients from the soil or the water and manufacture their own food using photosynthesis. In this way, it is energy from the sun that usually powers the base of the food chain.– An exception occurs in deep-sea hydrothermal

ecosystems, where there is no sunlight. Here primary producers manufacture food through a process called chemosynthesis.

TROPHIC LEVELS

2. Consumers - (heterotrophs) cannot manufacture their own food, and need to consume other organisms. They are usually animals. Animal that eat primary producers, such as plants, are called herbivores. Animals which eat other animals are called carnivores, and animals which eat both plant and other animals are called omnivores.

TROPHIC LEVELS

3. Decomposers (detritivores) break down dead plant and animal material and wastes and release it again as energy and nutrients into the ecosystem for recycling. Decomposers, such as bacteria and fungi (mushrooms), feed on waste and dead matter, converting it into inorganic chemicals that can be recycled as mineral nutrients for plants to use again.

TROPHIC LEVELS

• In real world ecosystems, there is more than one food chain for most organism, since most organisms eat more than one kind of food or are eaten by more than one type of predator. A diagram which sets out the intricate network of intersecting and overlapping food chains for an ecosystem is called its food web.

FIRST TROPHIC LEVEL

The plants in this image, and the algae and phytoplankton in the lake, are primary producers. They take

nutrients from the soil or the water, and manufacture their

own food by photosynthesis, using energy from the sun.

SECOND TROPHIC LEVEL

Rabbits eat plants at the first

tropic level, so they are primary

consumers.

THIRD TROPHIC LEVEL

Foxes eat rabbits at the

second trophic level, so they are secondary

consumers.

FOURTH TROPHIC LEVEL

Golden eagles eat foxes at

the third trophic level, so they are

tertiary consumers.

DECOMPOSERS

The fungi or the earthworms feed on dead

matter, converting it

back to nutrients that primary

producers can use.

Desert

Taiga forest

Temperate forest