Ecological management

Ecological Management:    This is how organisms adjust themselves so as to be able to survive in their environment. It helps to maintain equilibrium in the ecosystem

Associations: (Biological Associations)

These are the interactions between two or more different types of organisms in an ecosystem. These can be beneficial, harmful or neutral to each of the organisms of the association

Types of associations

• Symbiosis
• Saprophytic

Symbiosis:  Symbiosis is the close association of two or more species of organisms

The relationship in a symbiosis may be

• temporary or permanent
• harmful, beneficial or neutral to one or more of the partners

Types of Symbiosis

• Parasitism
• Mutualism
• Commensalism

Parasitism: Parasitism is an association in which one organism (the parasite), lives on or in another organism (the host), deriving benefit from it and causing harm to the host

Types of parasites

• Ectoparasites: parasites like ticks,fleas, lice, leechesetc that live on the body surface of their host are known as ectoparasites
• Endoparasites: endoparasites lives inside the bodies of their hosts. Examples include the roundworms, plasmodium, trypanosome,ascaris,tapeworm.

Features (adaptations) of biological importance possessed by parasites

1. Parasites must
2. be able to cling on the host body surface
3. have boring organs which will enable it to enter the body of the host
4. be able to secrete enzymes to dissolve tissues, enabling it to make it way in the host body
5. have organs that can penetrate the body surface and absorb nutrient

Specific examples

Animal parasites (ectoparasites)

Ticks are example of ectoparasite found on dogs,birds, cattle as well as humans. The legs ofticks are covered with spiny hairs. A claw is found at the end of each leg. These structures help ticks to crawl up grasses and shrubs where they wait for their hosts. Special sensory structures called Haller’s organ are found on the first pair of legs which detects the body heat and carbon dioxide released by a potential host.

When an animal or a person brushes against the vegetation, the tick will drop onto the host and use it claws to cling unto the host.

The mouthparts of the tick consists of a chelicerae (singular: chelicera) which are mandibles that cut into the skin of the host as well as the hypostome, a feeding tube which penetrates the skin into the blood stream, drawing blood from the host

Barbs on the hypostome help the tick to secure firmly to the body surface of the host while they are feeding. The saliva of some ticks also has anticoagulation properties which prevents the host blood from clotting when they are having a blood meal.

STRUCTURE OF A TICK

(B)Animalparasites (Endoparasites)

The parasite Ascarislumbricoides (the common round worm) enters the human host through food contaminated with eggs of the worm. The eggs hatch in the small intestine of the host.

The larvae then burrow the intestinal wall into the blood circulation. They grow in the blood stream. Eventually, they make their way back to the intestines.

The adult roundworm attaches itself to the intestinal wall and feeds on blood or intestinal contents. It has a simple digestive tract where food enters through the mouth and exits through the anus.

Like the tapeworm, it has a cuticle covering on its skin to protect itself from the enzymes secreted by the intestinal wall.

The roundworm produces large numbers of eggs which are passed out of the host’s body with faeces. The large number of eggs ensures survival

ROUNDWORM ASCARIS IN THE HUMAN INTESTINE

STRUCTURE OF ROUNDWORM

(C) Parasitic plants: Cassytha is a complete plant parasite which lives on many host plants such as Diallumguinense. It sucks manufactured food from the host by means of suckers or haustoria.

CASSYTHA

Mistletoe is a semi parasitic plant which grows on orange, avocado pear etc. Mistletoe has green leaves for photosynthesis but absorbs water and mineral salts from the xylem tissue of the host.

MISTLETOE

MUTUALISM: Mutualism is the relationship between two organisms of different species in which each organism benefits from the interaction. If both partners cannot live without the other, the term obligate mutualism is used to describe the association.

Formerly, symbiosis was only applied to mutualism.

Examples of Mutualism are

1. Leguminous plants and nitrogen fixing bacteria (Rhizobium bacteria). The Rhizobium bacteria are found in the root nodules of leguminous plants. The bacteria obtain shelter, protection and carbohydrates from the plants and at the same time provides the plant with ammonium compounds which they obtain from nitrogen fixation

ROOT NODULES OF A LEGUMINOUS PLANT

• Fungi and algae in lichens. Lichen is an organism formed by the close association between a fungus and an alga species. An example of a linchen is the photoautotrophic unicellular Trebouxia and an ascomycete fungus.

The alga specie obtains protection, shelter, water and mineral salts from the fungus. The alga manufactures sugar by photosynthesis and the fungus uses part of the food

Other examples are; Protozoa (Trichonymphia) in the digestive tract of termites, microorganisms in the intestinal tract of ruminants,mycorrhiza (association between fungus and the root of higher plants), cattle and oxpecker bird (tick bird).

COMMENSALISM: Commensalism is the association between two species of organisms in which one specie (commensal) benefits but the other one (host) is unaffected.

Examples are;

(1) Sharks and Remora fish.

 The remora fish attaches itself to the shark through a modified dorsal fin which has a suction function. When the shark feeds, the remora fish also consumes the scraps of food particles that fall towards it. In this association, the shark gains nothing from the fish but the remora fish gets food, shelter and protection

THE REMORA FISH GAINS FOOD AND SHELTER FROM THE SHARK

(2)Epiphytes and trees

In rain forests, the epiphytes grow on the hollow of larger trees for support to obtain more sunlight for photosynthesis. However, the trees are unaffected in the association

ASSESSMENT

1. State the relationship that exists between
2. Tapeworm and Human beings
3. Cowpea plant and Rhizobium
4. Remora and Shark
5. Ox pecker bird and Buffalo
6. Ticks and Zebu cow

2(a)    Explain:

• Parasitism
• Commensalism

(b) Mention

(i) One fungal parasite of a plant and its host

(ii) One bacterial parasite of humans

(iii) The most recent viral parasite of humans