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Main topics • Habitat • The Physical Environment • The Biotic Environment • Ecosystem
Habitat • A habitat is the natural home of an organism where it lives and reproduces. • Some examples of habitats are ponds , rock pools, trees , and even the bodies of large animals where tiny insects or microscopic animals live. • A wide variety of living organisms is found in a habitat.
Habitat • A place is best suited to be the habitat of an organism if it offers the organism an ample supply of food, shelter from predators, protection from bad weather and a place to reproduce, nest or hibernate.
Habitat • Everything around an organism that affects its way of life is called its environment. • The environment of an organism can be divided into physical or abiotic environment and biotic environment.
Habitat • The study of interactions between living organism and their environment is called ecology.
The physical environment • The climate of a place plays an important role in the physical environment of that place. • The physical environment in turn determine the types of organism which will live there. • As the environment can never be best suited for every living in it some organisms have adapted to their environment by developing certain features which enable them to live successfully in their environment.
Light • All green plants use light energy from the Sun to make their own food . As other forms of life on Earth depend directly or indirectly on green plants for food, they are also dependent on light for survival. Light also enables many living organisms to see so that they move about find food and detect danger. • Some organisms such as earthworms prefer to stay in the dark. They have developed special features to live in a dark environment. Insects such as fireflies and deep-sea fish produce their own light to illuminate their prey, confuse their predators or attract their mates.
Temperature • The heat received from the sun greatly influences the temperature of a place. Most organisms are active at temperatures between 0°C and 45°C.However aquatic animals and marine plants can remain active at freezing temperatures of around -1°C. On the other extreme, certain invertebrates live in hot springs which have temperatures of about 50°C while some algae can grow in waters at temperatures of up to 80°C.
For most organisms , there is a minimum and a maximum temperature beyond which they cannot carry out their vital processes of life. There is also an optimum range of temperature within which they are most active. Shedding leaves and hibernating are two adaptive processes which have enabled plants and animals to live through cold winters Temperature also controls the process of reproduction in plants some plants will not develop seeds unless they are subjected to certain temperatures for a period of time. This explains why some fruits and flowers are seasonal.
Water is essential for life and is therefore present in the environment of every organism. For aquatic animals and plants, whether marine or freshwater, water is the medium in which they live. The distribution of land organisms corresponds closely to the distribution of water over the land surface. Organisms are in general most abundant where water is available . Tropical rainforests are conductive to life because they are warm and wet. More than half of all plant and animal species in the world live in tropical rainforests which cover less than 10% of the Earth’s land surface. Organisms living in dry places have special adaption to store water and reduce water loss. The cactus, a desert plant, has spines instead of leaves to cut down water loss through transpiration. It also has a thick stem to store water. Camels can go without water for weeks. They can drink a lot of water at one time and their body fats can break down to provide them with energy and metabolic water.
Minerals are needed by plants for healthy growth. Nitrates, for example, are used by plants to make proteins. Plants obtain minerals from the soil in which they grow. Minerals required by animals are usually obtained from their diet or from minerals dissolved in their drinking water.
Most organisms cannot survive in environments which are too acidic or alkaline. That is why acid rain can kill aquatic life in rivers and lakes; and trees in the forests. Freshwater organisms live in fresh water with a pH of about 7. Marine organisms live in the sea with a pH value of about 8. Like aquatic plants, land plants are affected by the pH value of the soil . Most plants grow well in neutral or slightly alkaline soils. However, some plants such as the pineapple and cotton plant grow best in acidic soil. A pHValue is a whole number in the range of 1 to 14 which describes the measure of alkalinity or acidity of water soluble substances. If the pH level of any water soluble substance is 7, it is neutral and not considered as an acidic or alkaline substance. The pH value of water determines the types of aquatic organisms that can live in it.
Most organisms need oxygen for respiration . Land organisms take in oxygen from the air while aquatic organisms take in oxygen that is dissolved in the water. Warm , polluted water contains less dissolved oxygen than clean , cool water . Certain species of fish such as the lungfish and the guppy adapt themselves in water with little dissolved oxygen by gulping gaseous oxygen directly from the air. The rat-tailed maggot can live in badly polluted water because it can get oxygen from the air using its long breathing tube.
The Biotic Environment • No man is an island . This is not only true for man; it is also true for other organisms. Every living organism interacts with other organisms by feeding on them , competing with them for food ,water , light, air and minerals or by providing them with shelter and protection.
The most common of these interactions involves food. Herbivores are animals that feed on plants . For example grasshoppers and deer feed on grass; butterflies and humming bird feed on the nectar of flowers; caterpillars feed on leaves ; and some monkey feed on fruits.
Carnivores are animals that feed on other animals. Tigers, leopards, lion and eagles are carnivores.
Omnivores are animals that feed on both animals and plants. Bears, raccoons and crow. Human beings are also omnivores .
Scavengers are animals that feed on dead organic matter. Vultures are examples of scavengers
Camouflage is a pattern or colouring that disguises an organism or blends it with its surrounding so that it can hide from its predators or in the case of predators, creep up unseen on its prey. The chameleon , for example , is the master of disguise among animals because it can change its colour very quickly to blend with its surroundings. The poisonous stonefish has a speckled and lumpy body that blends itself with the stones on the seabed, waiting to grab its passing prey. Some butterflies have patterns which look like eyes on their wings to fool their wings to fool their predators. Some organisms have secretion that are poisonous to protect themselves from predators. Millipedes and caterpillars, for example, produce secretion that can cause blisters or itchiness on the skin of their predators. Some caterpillars have bright colours to warns their predators that they are poisonous. Predators are animals that hunt other animals for food. The animals which are hunted are their prey. For example, a lion is a predator and zebra is its prey. Predators usually have strong jaws, sharp teeth and claws to hunt and kill their prey. Eagles have good eyesight to track their prey and strong, sharp claws and beaks to catch and kill them. Some prey have developed certain forms of protection to escape detection by predators. The most common form of protection is camouflage.
Another example of mutualism is seen between the oxpeckers and large animals. Oxpeckers are birds that peck on the skin of large animals in search of ticks or blood-sucking insects. The large animals provide the oxpeckers with food while oxpeckers get rid of pests on the large animals’ skin. Mutualism is a relationship between two organisms in which both benefit. The crown fish and sea anemone, for example, benefit from each other by being together. The sea anemone provides shelter and protection for the clown fish. In return, the clown fish brings bits of food to sea anemone and even lures larger fish to its stinging tentacles.
There exists another kind of relationship between two kinds of organisms in which one benefits while the other neither benefits nor is harmed by it. This type of relationship is called commensalism. It exists between the remora fish and the shark. The remora fish attaches itself to a shark and feeds on food scattered by the shark. The shark neither benefits from the remora fish nor is harmed by it.
Parasitism is a type of relationship involving two kinds of organisms, the parasite and the host. The parasite benefits by living in or on the body of the host. In return, the host is harmed by the parasite. Ticks live on the body of dogs as parasites, feeding on their blood. The removal of blood brings harm to the dog.
Bacteria which cause cholera and tuberculosis are parasites that harm our body. Bracket fungi are parasites and draw water and minerals from the tree they live on. The Rafflesia, a plant found in Southeast Asia, is a parasitic plant.
A population is made up of one kind of organism living in a habitat, able to interbreed and produce its own kind. Different populations of plants and animals living together in the same habitat make up a community. When different communities interact with one another and their physical environment, they form an ecosystem. Deserts, seashores, mountains, rivers, oceans, grasslands and rainforests are some of the world’s ecosystem. Earth itself is a huge ecosystem.
In a tropical rainforest, populations of macaws, toucans, spider monkeys, sloth and others which live near the tree tops called the canopy of the forest, form a community. Another community of organisms, made up of populations such as squirrels, chimpanzees and tree frog, live in the cooler and shadier part below the canopy called the understorey. Populations of ants, jaguars, fungi, mosses and gorillas form the community on the forest floor. These different communities interact with one another and their physical environment to form the tropical rainforest ecosystem.
Important points: A habitat is the natural home of an organism where it lives and reproduces. Every habitat has its own physical and biotic environment. Light energy is used by plants to carry out photosynthesis. It is also used by animals to carry out daily activities e.g. finding food. Temperature affects the growth, activities and survival of living organisms. Some animals hibernate and some trees shed their leaves during winter. Water is needed by all living things. It dissolves nutrients so that plants can absorb them and provides a habitat for aquatic life. Minerals in the soil are absorbed by plants which then supply them to animals. The pH value of the soil or water determines the types of organisms that can live in or on it.
Important points: • 8. A population is a group of organisms of the same species which live and reproduce in the same habitat. • 9. Different populations form a community. • 10. Different communities living in a habitat interact with one another and with their physical environment to form an ecosystem. • 11. Living things in a habitat form the biotic environment. They depend on another for food, shelter and protection. • 12. The relationship between organisms include: • Predator-prey relationship • Mutualism • Commensalism • parasitism
