Living things interact with each other and their environment in various ways to survive. The document provides examples of interactions between aquatic organisms, including plants obtaining minerals from soil and oxygen from photosynthesis while animals obtain oxygen through respiration and carbon dioxide for photosynthesis. Predator-prey relationships between big and small fish and birds are also described. Overall interactions create balance and equilibrium within ecosystems.

5. Interaction in an environment
1. Living things interact with each other and with non-living things in order to survive.
2. The interaction between living things and non-living things lead to balance in an
ecosystem.
3. The example of interaction between living things and non-living things is shown below.
(a) Aquatic plants obtain mineral salts from the soil in the pond.
(b) Aquatic animals depend on aquatic plants to supply oxygen for the process of
respiration.
(c) Aquatic plants depend on aquatic animals to obtain carbon dioxide for
photosynthesis.
(d) Small fishes and tadpoles eat aquatic plants.
(e) Big fishes eat small fishes.
(f) Kingfisher eats fish.
(g) Water lettuce, water hyacinth, lotus and land plants obtain sunlight for the process
of
photosynthesis.
4. Interaction between living things and non-living things is important as it maintains
(a) balance in a environment ( the number and types of living thing within
the environment remain
the same ).
(b) balance in the carbon and oxygen cycles ( oxygen and carbon dioxide content in
atmosphere
remain the same ).

6. (A) The various forms of interaction
1. Living things interact among themselves in order to obtain food and protection.
2. Interaction may involve animal and animal, plant and plant or animal and plant.
3. Interaction between living organisms in an ecosystem will :
(a) Create equilibrium in the environment.
(b) Control the size of a population in a community.
4. There are three types of interactions among organisms :
(a) Predator-prey
(b) Symbiosis that consists of commensalism, mutualism and parasitism.
(c) Competition.
5. Predator-prey relationship.
(a) The animals that hunt other animals for food are called predators, while the hunted
animals
are preys.
(b) The predators which are carnivores have powerful jaws, sharp and strong teeth, good
stereoscopic vision, sharp claws or hard and strong beaks.
(c) The preys have a wide field of monoscopic vision to detect predators or are able to
camouflage
with their surroundings in order to escape from the predators.
(d) The examples are tigers (predators) and horses (preys), eagles (predators) and rabbit
(preys).
(e) Diagram 4.1 shows the predator-prey relationship.

7. Symbiosis
1. In symbiosis, different organism live together in a close relationship.
2. In symbiosis, one organism always benefits by receiving food, a place to stay and
shelter. The other
organism may benefit, be at a disadvantage or is not affected.
3. There are three types of symbiotic relationship, i.e. commensalism. parasitism and
mutualism.
Commensalism
1. Commensalism is a relationship between two organisms. One organism benefits from
the other. The
second organism is not adversely affected by the relationship.
2. For example, the stag horn fern grows on a tree. This helps it easily obtain sunlight. The
plant that it
grows on is not adversely affected.
3. Examples of plants that live on trees to obtain sunlight are
(a) the stag horn fern
(b) the money plant
(c) the pigeon orchid
(d) the bird's nest fern
4. Examples of animals that live on other animals to obtain food that fall out of the host's
mouth, as
well as for shelter and transport are
(a) barnacles that live on the shells of crabs, cockles or snails
(b) remora fish that live on a shark

8. 1. Parasitism is another type of interaction between two
organism. Only one organism benefits. The
other organism is negatively or adversely affected.
2. A parasite is the organism that lives on or inside the
other organism. The host is the organism on
which the parasite lives.
3. The host is negatively affected by this interaction. The
parasite may even kill the host.
4. A parasite obtains food, shelter and transport from the
host.
5. For example, a tick that lives on a host feeds on the
host's blood.
6. Other examples are
(a) stem borers and oil palm leaves
(b) tree barnacles and trees
(c) aphids and mustard plants