Chapter 18 - Organisms and their Environment

Primary producers

________ are photosynthetic organisms (autotrophs) that are able to convert light energy from the Sun to chemical energy that can be transferred from one organism to another within the ecosystem.

Sludge

________ undergoes a process of bacterial digestion to reduce the amount of organic matter and the number of disease- causing microorganisms present.

Green plants

________ convert atmospheric carbon dioxide into glucose during photosynthesis.

Decomposers

Organisms that obtain their energy from non- living organic material such as faeces, fallen leaves and dead organisms.

pollution

They are prone to overfishing and ________, which could lead to an imbalance in the ecosystem.

Food chains

________ seldom have more than 5 trophic levels as less energy is available at the higher trophic levels.

indiscriminate logging

The ________ without sufficient reforestation has led to many environmental and ecological problems such as: (a) The ‘ slash and burn practice used to clear forests for agriculture releases a large amount of carbon dioxide which contributes to global warming.

Ecology

the study of the interactions between organisms and the interactions of these organisms with their environment.

single tree

A(n) ________ can support a large population of aphids.

Inorganic substances

________ from industrial waste include: leached nutrients and fertilisers (nitrates and phosphates) from farmland, ammonia, sulfur dioxide from power plants, and heavy metals.

Carbon dioxide

The gas returned to the atmosphere when cellular respiration takes place in living organisms.

solid matter

The ________ left behind from the sewage treatment process is known as sludge.

Organisms

________ at each trophic level pass on much less energy to the next trophic level than they receive.

Pyramid of biomass

A pyramid that shows the dry mass of organisms at each trophic level in a food chain.

inorganic nutrients

They can also convert ________ in the soil to organic nutrients that can be transferred up the food chain.

Water pollution

occurs when pollutants are discharged directly into water without undergoing treatment.

Food webs

interconnected food chains

Energy

________ enters the ecosystem from the outside.

green plants

When the ________ and animals die, decomposers break their organic matter down into carbon dioxide and other simple substances.

Habitat

The place where an organism lives

Population

A group of individuals of one species that live in a particular habitat

Community

All the organisms that live in a particular habitat. It consists of populations of organisms that live close enough to interact with one another.

Pyramid of numbers

The pyramid which shows the population of each trophic level in a food chain.