Learning Objectives
After studying or reading this, you should be able to:

1) Outline the general characteristics of aquatic and terrestrial habitats.

2) Explain the effect of abiotic and biotic factors on life in aquatic and terrestrial habitats.

3) Explain how organisms in aquatic and terrestrial habitats are adapted to their habitats.

4) Identify the components of a food chain, food web and ecological pyramids.

5) Explain how food chains and food webs can be determined.


Aquatic Habitat

The physical environmental characteristics

1) There is normally slight temperature change with depth.

2) Light penetrate through the water body. There is a significant seasonal variation.

3) In estuaries or lagoons tidal activities give rise to high and low tide level.

4) The marine physical environment is characterized by waves, tides and oceans.

5) There is a general increase in pressure at the rate of one atmosphere per ten meters. In the estuarine aquatic habitat, the depth of the water is relatively shallow.

Chemical Environment Of The Aquatic Habitat

1)There is dissolved oxygen in all parts of the water but greater at the surface.

2) In the marine environment, the sea water has a relatively high salinity or salt content.

3) The aquatic environment become acidic whenever there is an increase in the carbon dioxide content in the atmosphere when it rains. This may affect the organism in the water body.

4) The aquatic habitat especially the sea water contains dissolved mineral salts mainly sodium chloride and many kinds of dissolved ions such as calcium, magnesium, phosphate, sulphate potassium, sodium, iodide, nitrate bicarbonate, and chloride.

5) Minerals and nutrients are scarce or dilute within the water medium as compared with drier soil.

Photosynthetic Organisms in the Aquatic Habitat

1) Photosynthetic organisms (water lettuce, duckweeds, water ferns etc) are found on the surface of the water so that they can get enough sunlight.

2) The white mangrove, Avicenia sp. occur in areas of high salinity and they are able to make use of the salt water.
They have broader leaves.

3)  The aquatic photosynthetic plants have broader leaves that are firm or leathery but flexible enough to resist tearing by wave action.

4) Woody aquatic plants found in riverine habitats have flexible branches so that when water runs over them, the leaves can be dragged through the water with relatively little resistance to tearing.

Characteristics of animals in the aquatic environment

1) Aquatic animals have streamlined body which reduces friction as, the animal moves through water.

2) Most aquatic animals have smooth, almost furless body that enables them to move through the water without friction.

3) Aquatic birds have long necks that keep the bodies of wading birds out of the water when feeding. The long neck helps the birds to reach the water or below it for food.

4) The eye of the aquatic animals are positioned on top of the head to allow animals to hide (almost fully submerged in water) and still detect predators or prey above the water.

5) The nostrils of most aquatic animals close when they go under the water.

6) Aquatic animals have transparent eyelid cover that covers the eye when they are swimming under water.

7) Aquatic animals have blubber (thick layer of fat or oil stored between the skin and muscles of the body that provides insulation.

Geological features of aquatic habitat
       Geologically, an aquatic habitat may be rocky, muddy or sandy. Aquatic habitats may also be Swampy. All these geological features determine the type or organisms that can live in the habitat.

General characteristics of photosynthetic organisms in terrestrial habitat

1) Photosynthetic organisms in the aquatic habitat have the following characteristics. '

2) They have green leaves that they use to trap sunlight for photosynthesis.

3) They have well developed root system for absorption of mineral salts and anchorage.

4) Trees have slender, smooth and straight trunks with thin bark especially in the forest habitat.

5) Some small plants (epiphytes) grow on other tall trees so that they can receive light to photosynthesize.

Physical environment of Terrestrial Habitat

The terrestrial habitat have the following physical environmental characteristics:

1) The forest habitat has a constant high humidity

2) The effect of temperature is greatly felt in the terrestrial habitat than in aquatic habitat.

3) The forest floor is often devoid of light and there is very little vegetation.

4) In terrestrial habitat, the effects of rainfall are very obvious than in water habitats. The variation in the amount of rainfall results in drought and floods.

5) In terrestrial habitats, the wind affects the rate of evaporation at a place. increase in wind strength increases the rate of evaporation and vice versa.

6) The altitude also affects plants and animals on land a great deal because as altitude increases, there is a decrease in temperature in a wind and vice-versa.

Chemical environment of terrestrial habitat

The chemical environment of a terrestrial habitat may include the following:

1) Carbon dioxide and oxygen concentration.

2) Respiration and photosynthesis are balanced in the world as amount of oxygen equals amount of carbon dioxide.

3) The acidity and alkalinity of soil from place to place differ and this affects plant growth on the soil. In waterlogged clay soil, the acidity of the soil tends to be greater than the sandy soil.

Geological features
      The geological features of terrestrial environment differ from place to place. A habitat in a terrestrial environment may be mountainous, slope gently or steeply or be a flat land. All these features affect the organism that inhabits such habitats. Animals therefore have a lot of adaptation that makes them fit to leave in habitats with different geological features in the terrestrial habitat.

Characteristics of animals in terrestrial habitat

In the terrestrial habitat, animals may have some of the following characteristics:

1) The arthropods develop exoskeleton which envelopes the body and prevent water loss.

2) Certain animals may go into a state of dormancy during the dry season especially in the savanna habitat.

3) Some animals (e.g. camels) have tissues  that are tolerant to water loss.

4) In most terrestrial habitat, fertilization is internal to avoid drying up of gametes.

5) The osmoregulatory organs are adapted to reduce water loss in some animals.

6) Some animals adopt protective colouration to resemble their backgrounds so as to escape predation.

General characteristics of terrestrial habitats

The Physical Environment

1) The environmental temperature of terrestrial environment is less stable than that of aquatic habitat.

2) The water. vapour pressure of the environment is frequently lower than the aqueous solutions in organisms.
Organisms therefore adapt a lot of mechanism to prevent themselves from dehydration.


As it has been said already in this book, abiotic factors are the physical factors of the environment and biotic factors are the biological factors.

Some of the major abiotic factors that affect organisms in the aquatic habitat include light, water currents, salinity, turbidity and depth of water pressure, oxygen concentration temperature and pollutant concentration.

Marine Habitat
  In the marine habitat, (oceans, sea and salt water lakes) the fishes tend to move down to the deeper part of the water when the light intensity is high. When the intensity of light is reduced, most animals move up to the surface of the water. The salinity of sea water is very high and all organisms that live in the sea water have special mechanisms that make them isonnic to the sea water to prevent dehydration.

The wave action of the sea is very high and swift in the intertidal zone. To survive periods buffeting by waves, organisms like the sea anemone and limpets have sessile habits. Sea weeds like Fucus and Luminary attach themselves firmly to rocks to avoid being swept by the wave action.

In the brackish or estuarine habitat (where seawater meets fresh water), the animals commonly found include crab, molluscs, shrimps, bivalves, etc.

Fresh water habitat (ponds, streams and rivers)

In the freshwater habitat, there is dissolved oxygen in all parts of the water but greater at the surface. During heavy rainfall, sediments are transported from the land to freshwater bodies and this increases the turbidity (cloudiness) and reduces the ability of light to penetrate to the deeper side of the water. If this happens continuously, plant and animal life in the habitat will be greatly disturbed.

ln freshwater habitats, pressure increases with depth of the water where an organism leaves therefore determines the pressure acting on it As a result of this, organisms live at certain depth of the water depending on their tolerance pistia, duckweed, salvinia spp to the pressure. In the freshwater, water plants grow in shallow water where they can receive sufficient sunlight to under go photosynthesis.

In streams and rivers, some of the smaller animals cling firmly against stones and rocks or hide among the vegetation in water to avoid being carried away by the water current. The Simulium larva may attach itself firmly to the surface of rocks by a hook to make it survive in the water.

Many aquatic plants (Crinum, Vallisneria, etc) have thin, flat and long leaves that present them a large surface area for maximum absorption. Carbon dioxide and minerals find there are those which can withstand salinity variation and they include prawns, grey mullet, the hairy mangrove crab, the fiddler crab, etc.

The white mangrove is among the plants that grow in this habitat. They have pneumatophores or breathing roots to enable them to exchange gases (CO and oxygen) in the atmosphere.

Mollusc and worms make burrows and live in shells to protect themselves against wave action.

Another aquatic plant, white water lily (Nymphaea) have waxy upper surface that prevents rainwater to settle on it and block its stomata with its sediments. The Nymphaea ' also have large air spaces in its leafstalks where oxygen may diffuse from the leaves to the roots.

Some fishes in the pond and lake (example: Tilapia, claries and Lobsters) have gills with which they breath and a swim bladder to assist them rest at any depth in the water.


Terrestrial habitats may be grouped as forest, savanna (grassland) and deserts.


A forest is a plant community in which trees are the dominant species.

In the tropical rainforest, the rainfalls throughout the year and this influence the growth of almost all plants. Rainfall makes water available to plants as the plant roots absorb them from the soil.

Too little or too much rainfall also adversely affects plant life in a habitat. The rainfall also provides the right condition for almost all organisms in the soil to carry out their activities.

Termites start new colonies during the rainy season when the soil is soaked with water and made soft.

Rainfall also creates habitat (ponds, pools, etc) for tadpoles, algaes, mosquitoes, larvae, etc.

Almost all plants need light in order to manufacture their own food. Some climbing plants (stems) like the yam. cucumber, morning glory flower, etc all climb other plants so that they can position their leaves in such a way that it can receive maximum amount of light for photosynthesis.

Most animals; termites swarm during the night only to avoid being preyed upon by flying birds.

Epiphytes such as ferns and orchids are also found at various levels on the trunk and branches so that they can receive enough sunlight.

Temperature as an abiotic factor influences the growth of frogs and houseflies in a habitat. Life activities of micro4organisms and small animals in the forest soil is also influenced by increase in temperature.

Savanna (Grassland) habitat

This is a plant community in which grass species are dominant. There may also be some few shrubs and small trees in the savanna habitat. The vegetation in the savanna mostly rely on rainfall and the duration of the dry season. The savanna experiences high temperatures all year round. Plants like Cactus and Opuntia therefore have their leaves reduced into spices to reduce water loss to the environment due to low humidity. Other plants which are shorter and thorny have narrow leaves that reduce water through transpoevaporation to its barest minimum. With this behaviour they are able to withstand high temperature and low humidity characteristic of the savanna.

Termites in the savanna also build termiterium that provides very cool temperature in the midst of high temperature.

The effect of biotic factors on aquatic habitat

An organism’s biotic environment refers to all the other organisms with which it comes into contact. Organisms may interact in many ways such as depending on another for food or just for protection or shelter. '

Aquatic habitat
    In an aquatic habitat, one organism may live on another (the host) and benefit whilst the host does not gain or loss The gains may be in the form of shelter, free transport, food , or protection. The clownfish (tropical fish) live among the deadly tentacles of the sea anemone. The tentacles quickly paralyzes other species of fishes, protecting the clown fish against predators.

Another example of biotic factors or relationship is between the small fish, remora and the shark. The remora fish live as a commensal on the shark attached by its suckers. When the shark feeds, the remora detaches itself and feed on the left over food from the shark. All the above relations are examples of commensalism.

The hermit crab may also leave on the sea anemone. In this relationship, they all benefit

In the freshwater habitat, the sunfish may eat water flea. Other fishes also feed on planktons.

In the marine habitat the shark (predator) may feed on other smaller fishes (prey) for its survival.

Effect of biotic factors on terrestrial habitat
In the terrestrial habitat, organisms affect one another in a number of ways.

Plants with weak stem may use other plants for support in order to reach light. In the forest habitat herbivores like grasscutters may feed on plants and in the process destroy them.

Epiphytes such as ferns may grow on another plant like the palm tree without causing any harm to it.

In the forest, very tall trees that form canopies may provide shelter or shade to shade-loving animals and plants. Flying insects like butterfly may also move from flower to flower and in the process help pollinate them. Birds and other mammals eat the fruit of plants and as they move about help in dispersal of the seed in the fruit.



These are features of organisms which structurally, physiologically and behaviourally make them fit for life in their particular habitats and improve their chances of survival.

Aquatic Habitat

Organisms living in aquatic habitats have various adaptations that ensure their survival in their various habitats.

Organisms in freshwater environment are faced with a number of limiting factors such as oxygen stratification, temperature stratification, light penetration, current or surface wave action, etc.

1. Some animals attach themselves to Stationary objects by adhesive structures like suckers (leech), hooked claws (mayfly nymph) and fat (water snail).

2. Freshwater plants have chloroplast even 1n epidermal cells of leaves and stems of submerged.

3. Freshwater animals have different but relevant feeding adaptations. The Diptera larvae (simulium) have a “head net” for straining. food from the water.

4. Almost all freshwater animals have a stream-lined body that enables them to swim in the water:

Aquatic Plants

1. Some insect in the freshwater aquatic habitat such as Carixa (water boatman), Dystiscus (diving beetle) and Gyrimus have their last pair of legs modified in such a way that they can swim.

2. Freshwater fishes like Tilapia and Claria (cat-fish) have gills for breathing and a swim bladder that makes them buoyant to inhabit anv depth in the water.

Marine Habitat
Organisms in the marine habitat are adapted to their environment in different ways:

1. Mollusc and worms may hide in their shells and sometimes make burrows to protect them against wave actlon and predation. In the littoral zone, sea anemones and barnacles have adaptation to do filter feeding.

2. Many organisms like the crustaceans and the molluscs have spices and supporting structures that they can use to attach to a stationary object to avoid being swept away by the waves action.

3. Animals that inhabit the sandy beach get their food by burrowing through the sand and ingesting the substate that results from it.

4. Most marine plants have salt secreting glands and thick cutin on the surface of the leaf to maintain a very high osmotic pressure.

Terrestrial Habitat .

Terrestrial organisms may have various forms of adaptation to enable them live successfully in their habitat.
The adaptation may include the following:

1. Some animals go into the State of dormancy during the dry season and come out during the rainy season. The. king fishes are able to survive dry conditions in swamps where they live by burrowing into the bottom and encasing into a cocoon. They only come out during the rainy season.

2. The arthropods have jointed limbs and vertebrates, possess pentadacty limbs to help them move effectively on land.

3. The cuticular membrane in insects, feathers in birds and the skin membrane.

4. In the forest habitat, the reptiles have opposable limbs, prehensile tail (chameleon) for climbing. The geckos have sticky pads on their palms for climbing and snakes have elongated bodies that enable them to twist around branches of trees.

5. Some animals including the camel have tissues that are tolerant to water loss. Some terrestrial animals, exhibit protective colouration that enable them resemble their background so as to escape from their predators. Chameleons are capable of changing their colours to resemble a variety of backgrounds.

6. Some plants that grow in the savanna habitats have thick and corky bark to protect them during bushfires and reduce transpo-evaporation.

7. Forest plants have adaptions for climbing such as twinning, scrambling and the possession of roots hooks.


Food Chain
The linear transfer or transmission of energy containing  material from one group 0f organisms to others in any habitat is described as food Chain.

Example: in a terrestrial habitat, a food chain can be represented as:

Grass -> grasshopper -> toad-> snake -> hawk.

Grass -> grasshopper -> praying mantis -> Lizard.

In a marine habitat a simple food chain may consist of:
Diatoms -> copepod >small fish ) Big fish

Specifically. it may look like this: Chactoceros -> Acartia -> fthmalos -> Shark

In freshwater environment, it could be

Diatom -> Paramecium -> water flea -> mud fish -> Cymnarchus.

A food chain can therefore be said to be feeding relationship in an ecosystem in which energy is transferred from plants through a series of organisms by each stage feeding on  the preceding stage and providing food for the  succeeding stage.

In constructing a food chain, this pattern should be your guide:
Producer -> Primary consumer -> secondary tertiary -> tertiary consumer

Food web
In a community, a food chain rarely exists since consumers do not feed on one kind of food. Often, a particular food item is eaten by more than one consumer. A food web can therefore be said to be a network of interrelated food chains. A food web is interwoven and interconnected feeding relationships of an ecosystem. It is made up of food chains that are interconnected.

The followmg terms should be taken nonce of:

1. Producers: This refers to green plants that manufacture their own food.
Producers always form the base of the food chain.

2. Consumers: This refers to organisms (animals) that eat plants or other animals for them to obtain energy.

3. Primary Consumers: This refers to herbivores (plant eaters) since they are the first consumers to feed on plant materials in a food chain.
Examples include; goats, parrots, etc.

4. Secondary Consumers: This refers to animals who prey on other animals for their sumval. They are flesh eaters. They are mostly carnivores. Some examples include. snakes, cats. etc.

Tertiary Consumers: These are animals that feed on secondary consumers.

Examples include: hawks, lions, etc. Other animals may feed on plants and animals for their survival. It must be noted that, omnivores can be both primary and secondary consumers in a food chain.

Decomposers: These refer to bacteria and fungi that breakdown dead and organicmaterials and absorb simple food materials that results from it to obtain energy.

In the ecosystem, they return essential nutrients stored in plants and animals back into the soil for the roots of the green plants to reabsorb them.

Pyramid of Numbers: The pyramid of numbers depicts the number of organisms at each trophic level. A pyramid of numbers is the representation of the numbers of organisms at different trophic levels in a food chain.

In pyramid of numbers, the number of individuals decreases as you move up the pyramid, and the size of the individual increases, as you move down.

The producers always occupy the broad base of the pyramid and tertiary consumers occupy the apex of the pyramid.
Pyramid of numbers

Inverted Pyramid: In certain instances, a singly but very large producer may support a large community of consumers. This results in what we call inverted pyramid.
Inverted pyramid

Pyramid of Biomass .
    Pyramid of biomass shows the total weight of organisms supported at each trophic of feeding level, The pyramid of biomass is measured in grammes per square . It is the most accurate representation of a food chain than the pyramid of numbers.

The pyramid can be constructed by weighing the total mass of organism at each trophic level in a food chain in a particular area and using the biomass. A more reliable and accurate results can be achieved by using the dry mass of organism. However, this method is destructive since organisms are killed before their values can be determined.
Pyramid of biomass

Pyramid of energy
    The flow of energy in feeding relationships can be represented by the pyramid of energy. This pyramid of energy depicts the amount of energy available at each trophic (feeding) level m a food chain in a particular area.

The pyramid of energy has the following merit over the others:

1. It makes it possible to compare pyramids of different ecosystems.

2. It presents a more accurate results when studying trophic levels.

3. It makes it possible to look at how efficient transfer of energy between trophic levels is.

However, one demerit is that it, is very tiresome to obtain data for the construction of the pyramid.

ln constructing the pyramid of energy, the energy value of each organism is determined by measuring the heat produced when a known mass of organism at each trophic levels are burnt.

The pyramid of energy is measured in K/m  year . The unit reads as Kilojoule per meter squared per year.
Pyramid of energy

The following important points must be noted:

1. Inverted pyramids: ln inverted pyramids, the producer, a singly plant may support a large number of primary producers. Example: A single plant infested with parasites and the latter are parasitized by further parasites.

2. Net primary production: This is the energy contained in the producers which is actually available to the consumers.

3. Net secondary production: This is the energy contained in the consumer.

Methods of determining food chains and food webs

1. Dissection of gut examination
       In gut examination, an organism is trapped, killed and dissected. Samples of the content in the stomach is then obtained and analysed. This method gives a first-hand information about the organisms which a consumer feds on.

2. Direct Observation
     In this method, the feeding habits of organisms in a community is closely observed and the results obtained used to construct a food chain or food webs.

Have you ever seen a lizard feeding on a grasshopper before? What about a hawk trying to feed on a lizard? What does the grasshopper eats.

The information from this question can easily be used to build a food chain.


This is the method in which labelled radioactive food substances are incorporated or fixed into inorganic fertilizers and applied on the field.

These labelled fertilizers are absorbed by roots of the plants from the soil land fixed into the plant materials. The labelled radioactive food substances normally used are isotopes of phosphorus-32 or sulphur-35.

With the aid of sensitive counters. the path of the radioactive isotopes can be traced in the consumers. Usually, the primary consumers which are normally small herbivores first, followed by the predators.

lf conclusion can be drawn:

i) It may have eaten material from the plant.

ii) It may have consumed one or more animals that have already fed on the plant material.

Did you understand what you have just studied or read?

To make sure you have understood, ANSWER the QUESTIONS below:

1. State four structural features which adapt animals to a named natural habitat

2. Describe the method you would use to determine the density of a named plant species in a terrestrial habitat.

3. Explain the interdependence of plants and animals in a habitat.

4. a. Explain the statement adaptation of an organism to environments.

b. State the ecological importance of seaweed. . S.

5. a. Define the term adaptation.

b. Describe how plants are adapted
to the following habitats giving one example of a plant for each habitat.
i. Dry terrestrial habitat.  ii. Fresh water habitat.

6. a. State four ecological factors that are common to all habitats.

b. List the instruments that could be used to measure the factors named in (a).

7. a. Briefly describe how the crab is adapted to life in its habitat.

b. i. Four causes of food shortage.
ii. Four factors that affect population size.