4.1 Species, Communities and Ecosystems

Question 1

What is a biotic factor?

Answer 1

Any Material that has a significant biochemical function.

Examples are prey, soil bacteria, bugs, plants…

Question 2

What is an abiotic factor?

Answer 2

The physical environment of an ecosystem is known as an abiotic factor.
Examples are rain, soil type, temperature, oxygen level…

Question 3

What is a species?

Answer 3

a group of organisms that can interbreed and produce fertile offspring
Example: humans

Question 4

What is a habitat?

Answer 4

the environment in which a species normally lives or the location of a living organism
Example: tree canopy

Question 5

What is a population?

Answer 5

• Members of a species may be reproductively isolated in separate populations.
• a group of organisms of the same species who live in the same area at the same time

Question 6

What is a community?

Answer 6

populations of different species living and interacting with each other in an area
Example: forest of trees and undergrowth plants, inhabited by animals and rooted in soil containing bacteria

Question 7

What is an ecosystem?

Answer 7

a community and its abiotic environment

Exp: Pond/lake

Question 8

What is ecology?

Answer 8

the study of relationships between living organisms and between organisms and their environment

Question 9

What is a biome?

Answer 9

Biomes are divisions of the biosphere and are devided by their climate and topography. Rainfall and temperature are the two most important factors that determine the appearance of a biome

Question 10

What is an autotroph?

Answer 10

an organism that make their own carbon compounds from simple inorganic substance from the abiotic environment.

Question 11

What is a heterotroph?

Answer 11

an organism that obtains carbon compounds from other organisms

Question 12

What are three types of heterotrophs?

Answer 12

Consumer, Detritivore, Saprotroph

Question 13

What is a consumer?

Answer 13

heterotrophs that feed on living organisms by ingestion. (ie. an organism that eats other living organism)

Question 14

What is a detritivore?

Answer 14

heterotrophs that obtain organic nutrients from detritus by internal digestion. (ie. an organism that eats dead organic matter and digests them internally)

Question 15

What is a saprotroph?

Answer 15

heterotrophs that obtain organic nutrients from dead
organisms by external digestion. (ie. an organism that secrets digestive enzymes into dead stuffs and then suck up the juice)

Question 16

Example of a saprotroph?

Answer 16

Example fungi, mould, mushroom

Question 17

Example of detritivore?

Answer 17

Example earthworms

Question 18

What is a food chain?

Answer 18

A linear link from producer to consumer.
General form:
A →B → C → D indicates that A is being “eaten” by B, B eaten by C and so on (that is, the arrow indicates the direction of energy flow).
Each food chain should include a producer and consumers, but not decomposers.

Question 19

What is a food web?

Answer 19

A bunch of food chains interconnecting with each other

Question 20

What is quadrat sampling?

Answer 20

Quadrat is just a square thing used to sample the plants in the area (not for animals). The goal of using quadrat is so that ecologist can survey different area the same way in order to make comparison between 2 or more areas.

Question 21

What is a mesocosm?

Answer 21

Mescosm is a small area where parts of the natural environment are kept under controlled conditions.

Question 22

Why do we use mesocosm?

Answer 22

Advantages:
- Able to control variables and thus gives the opportunity to measure the degree of stability or extent of change in the community, and to investigate a precise impact of a disturbing factor

Disadvantages:
- Unrealistic

Question 23

What does a t-Test do?

Answer 23

It compares two means/averages

Question 24

What is Chi-square used for?

Answer 24

it is used to compare if what you observed is different from what you expected

Question 25

Compare the way in which autotrophic, heterotrophic and saprotrophic organisms obtain energy.

Answer 25

autotrophs use an external / non-organic energy source

(reject statements suggestion that energy is made)
(some) autotrophs use light / (some) autotrophs use photosynthesis
(some) autotrophs use inorganic chemical reactions / (some) autotrophs use chemosynthesis
heterotrophs obtain energy from other organisms
heterotrophs (usually) ingest food / consume food
saprotrophs obtain energy from non-living matter / dead organisms
saprotrophs digest organic matter extracellularly

Question 26

Describe a method for measuring the size of a population of plants using quadrats.

Answer 26

random positions for the quadrats
use of random numbers fro co-ordinates / other randomisation procedure
many repeats / quadrats
size of quadrat depends on size / density of plants
count number of plants in each quadrat
find mean number of plants per quadrat
multiply number per unit area by total area to obtain total population

Question 27

Describe what is meant by a food chain using an example with four named organisms.
(4)

Answer 27

food chains describe the feeding relationships between species;
Exp:
Carrot plant → Eastern Cottontail Rabbit → Red fox → Golden Eagle

Question 28

Why does an ecosystem have the potential to be sustainable over a long period?

Answer 28

• continual flow of energy
• nutrients are recycled
• removal of toxins
• conservations allows balance