Saturday X-tra
X-Sheet: 16
Local Environment Issues: Biotic and Abiotic factors
Key Concepts
In this session we will focus on summarising what you need to know. We will:
 Describe the various biomes and the animal and plant life.
 Explain and analyse the balance within ecosystems.
 Distinguish between biotic and abiotic factors and understand the impact of each.
Terminology & definitions
Abiotic: all non-living components in the biosphere, e.g., air, water, soil, climate.
Autotrophic: .when an organism is able to produce its own food using abiotic
components.
Biotic: all the living or dead components in the biosphere: animals, plants, microorganisms, paper, decomposed matter, etc.
Biosphere: it is the global sum of all ecosystems, and is the zone where all living
organisms live on earth.
Biome: the biosphere is divided into millions of biomes, based on the specific climate of
each region, where the climate determines the unique plant and animal species that live
and are adapted to survive in a region.
Carnivores: animals that eat only meat. They are generally predators, like lions, cheetahs
etc., in a specific environment.
Ecosystem: is the combined physical and biological components of a specific habitat
where animals and plants are interdependent on each other for survival.
Herbivores: animals that only eat plants, e.g., buck, cows, goats, sheet, rabbits etc.
Heterotrophic: when an organism is unable to produce its own food, and must eat other
organisms
Omnivores: animals that eat both plant and animal matter, e.g., humans, pigs, baboons.
Saprophytic organisms: organisms that live on dead organic matter because they are
able to decompose (break down) dead plant and animal matter.
Scavengers: animals that eat what is left over by predators. Examples are hyenas,
crayfish and vultures.
Photosynthesis: a process where plants use sunlight energy, water and CO2 from the
air, to produce organic compounds like glucose and inorganic compounds like O2.
Vegetation: the plant life that is found in a biome.
Diagrams
Producers
ECOSYSTEMS
Biotic factors
Abiotic factors
Plants
Air
Primary
consumers
Secondary
consumers
Water
Animals
Sunlight
Tertiary
consumers
X-planation
Soil
Decomposers
Temperature
Biotic Factors
Producers: plants are classified as autotrophic because they produce their own food
(Auto = on its own and Trophic = food). Plants use radiant energy from the sun, CO2 from
the air and H2O from the soil to produce nutrients and O2 during a process called
photosynthesis. When consumers eat the plants, energy from the sun in the form of the
nutrients moves from the plant to the consumer. For example, a locust eats a plant and is
then eaten by a bird. The energy goes from the sun (radiant energy) to the plant, from the
plant to the locust. The energy that is stored in the body of the locust, will be transferred to
the bird. This is the energy transfer system. Remember, energy can never be created or
destroyed – it can only be transferred.
Plants are classified according to where they grow:
 Hydrophytes: Hydro means water - plants that grow in water, e.g., elodea, water
lilies, seaweeds, algae.
 Mesophytes: Meso means middle/in between - plants that need moderate amounts
of water, light and temperature, e.g., the plants in your garden.
 Xerophytes: Xero means dry/waterless - plants that grow in very dry regions, e.g.,
fynbos, cacti and aloes.
Consumers: animals are classified as heterotrophic because they cannot produce their
own food, and consume plants or animals that eat plants. Consumers are divided into
three groups:
o Primary consumers: animals that are herbivores and obtain their energy by
eating plants only, for example, antelope, buck, sheep, weaver birds, chickens,
rabbits etc.
o Secondary consumers: animals that are carnivores and omnivores. Carnivores
obtain their energy by eating other animals, for example, cats, lions, wild dogs,
eagles. Carnivores are often predators and catch live prey, kill them and eat them.
Omnivores eat plants and animals, for example, humans, pigs, parrots.
o Tertiary consumers: animals that feed on both primary and secondary consumers.
They obtain their energy by eating other animals, for example, snakes, crocodiles
and hawks. Scavengers eat what is left over by predators, for example, hyenas,
crayfish and vultures.
Decomposers: decomposers are classified as saprophytic because they live on dead
organic matter. They are able to decompose the dead plant and animal matter into
nutrients. They obtain energy by breaking down the organic compounds in the matter and
absorbing them. Algae, fungi and bacteria are examples of decomposers.
Abiotic factors
Abiotic factors include all the non-living components of the environment, e.g., sunlight,
temperature, air, water and soil. The biotic factors require abiotic factors to survive.
Abiotic factors are grouped into:
o climatic factors – temperature, water, light and gases
o edaphic factors – soil types, pH and humus content
o physiological factors – aspect (position of the area in relation to the sunlight),
slope and altitude.
X-ample Questions
Question 1
Fynbos is a major vegetation type in the Western Cape. This vegetation is unique and
indigenous to the region. In the year 2000, legislation and projects were announced to
combat the spread of an invasive alien species, called the Port Jackson Willow, into the
fynbos. Data available is shown in the graph below.
In 2005, a group of grade 12 learners conducted an investigation to evaluate the success
of these projects launched in 2000. A 1 km 2 area was selected in the same area used in
1995 and 2000 and divided into six sample areas (quadrants). The data below was
recorded by the learners. Study the table and answer the questions that follow.
1.1. Define the term indigenous species.
(2)
1.2. Why did the learners choose a study area of 1 km2?
(1)
1.3. From the table calculate the total number of:
(a) Fynbos plants
(b) Port Jackson Willow plants
1.4. Compare the number of plants in 1995, 2000 and 2005 and write down your
observations.
1.5. What can be concluded from the results of the latest investigation?
(2)
(4)
(2)
(Taken from NSC Life Science Prep Examination 2008 Paper 2)
Question 2:
Read the text below and answer the questions, which follow.
OVER-FISHING OF COD
One of the most important species of fish caught for food in the North Sea, is cod.
They live in shoals, are active hunters and feed on other fish such as herring, and on
squid. Cod only begin to breed when they are about 3 to 4 years old. By this time they
are about 50 cm long. Unfortunately, over-fishing of cod is slowly reducing the cod
population.
1.
2.
3.
Explain TWO consequences to the ecosystem if the cod population becomes
extinct.
(4)
Explain THREE management strategies that could be employed by the countries
around the North Sea to prevent the cod population from becoming extinct.
(6)
Explain ONE problem that could result from any of the management strategies
that you described in QUESTION 2.
(2)
(Taken from NSC Life Science Feb/March Examination 2009 Paper 2)
X-ercise
Choose the correct answer for each of the following questions.
1
A living organism found only in a particular region is referred to as
being …
A extinct.
B endangered.
C indigenous.
D alien.
2
Which of the following may be reasons for the exploitation of
natural resources?
1 Poverty and shortage of food
2 Use of indigenous plants for medicinal purposes
3 Use of wood to generate heat energy
A
B
C
D
3
1 and 3
1 and 2
2 and 3
1, 2 and 3
The diagram below illustrates the relationships between organisms in an
ecosystem. Which change would most likely reduce the population size
of the carnivorous fish?
A
B
C
D
an increase in the autotroph populations
a decrease in the duck population
an increase in the raccoon population
a decrease in pathogens of carnivorous fish
4 Which method of controlling populations of mosquito most likely involves the
least risk of causing damage to the environment?
A draining swamps where mosquitoes deposit eggs
B spraying adult mosquitoes with pesticides from airplanes
C releasing more predators of mosquitoes native to mosquito habitats
D spraying oil on wet areas where mosquitoes breed
5
Study the food chain shown below.
algae 
snail 
fish 
human
Which of the following is MOST UNLIKELY to happen if humans would exploit
the fish population?
A
An increase in algae and snail populations
B
A decrease in fish as food for humans
C
An increase in the snail population
D
A decrease in the algae population
Answers to X-ercise questions
1.
2.
3.
4.
5.
C
D
B
B
A