ESS 2.1 - 2.3 Quiz

Density-dependent factors, by bringing the population size back to equilibrium, act as a _________ feedback mechanism.

• negative

• positive

• reverse

• inverse

Given the fact that humans can eat a variety of food sources (both plant material and meat), state what type of organisms they are.

A group of organisms of the same species sharing the same habitat at one time and capable of interbreeding may be described as:

The graph which represents only exponential growth of a population is a _______ shaped growth curve/graph? Give only a single letter or word as your response

What is the word used to describe a  non-mutualistic relationship between species, in which one species lives in or on another species (the host), causing it harm.

What is another name for a primary producer that means self-feeder? 

Answer explanation

Primary producers are also called autotrophs which means self-feeder. This is due to the fact that plants can use solar energy to convert inorganic compounds into food.

In a diagram or model representing energy or productivity flows, such flows are usually represented by ______ .

State the name of a chemical capable of bioaccumulation and biomagnification. Note that it is often used to prevent the spread of malaria.

Answer explanation

Explanation:

DDT is a persistent insecticide, used extensively in the 1950s and 60s to prevent insect damage and improve crop yield. It was responsible for the deaths of many bird species at the top of the food chain, due to bioaccumulation and biomagnification. DDT was brought to the world’s attention in Rachel Carson’s “Silent Spring” and is still used in India to kill the mosquitoes that spread malaria.

Certain chemicals may be retained in body tissue of organisms, such as fat, and not broken down. This process is called:

• biomass

• biomagnification

• bioaccumulation

• biocomposition

Answer explanation

Bioaccumulation is a process in which persistent chemicals accumulate in an organism’s body tissue (usually fat) and are not broken down. They are then passed along a food chain to the subsequent organisms and their concentration increases. This is then called biomagnification.

Pyramids of numbers, productivity and biomass are models used to represent quantitative differences between trophic levels of a single ecosystem. Which pyramid will always show a decrease along the food chain?

• Pyramid of numbers

• Pyramid of productivity

• Pyramid of biomass

• Pyramid of differences

Answer explanation

Pyramid of productivity (energy) will always show a decrease along a food chain, while the other types of pyramids will occasionally vary in shape. This is due to the fact that with each trophic level, energy is dissipated and the entropy of a system increases. Hence why, there is gradually less energy available to the subsequent organisms along the food chain.