Predators and Parasites (essay) Laurence Pringle

Predators and Parasites

Laurence Pringle

The living things in an ecosystem affect each other in many ways.  The consumers that kill other animals for food are called predators. The lion, the tiger, the wolf and man are predators.  Predators are stronger and bigger than their prey animals. But in number, they are fewer than the prey animals.  Studies show that predators work hard to get a prey animal. For example the tiger makes twenty to thirty unsuccessful attempts before it catches a prey animal.

Parasites are usually smaller and more numerous than their hosts. These organisms live on or in other  living things, which are called hosts.  Parasites often spend a lifetime with the hosts. The parasite gets food and sometimes shelter, while the host gets nothing and may suffer in someway from the relationship. There are many parasites such as fungi, bacteria, flatworms, insects, ticks and mites. Parasites are an important part of all communities, and like predators, often control the population of other organisms in a community.

The idea of using parasites and predators to control pests is known as biological control.

Man has been using this ecological knowledge by bringing parasites or predators into an area  to  kill pests that destroy crops. Sugar cane planters in Jamaica brought mongooses from India to kill rats because it had been destroying sugarcane crops. But mongoose began to eat rat and after that began eating native birds and animals such as snakes, lizards and other land crabs and began to eat sugarcane. Similarly house sparrows from England were brought to the USA to control elm spanworms in the park. But the sparrows began to compete with the native birds and it became a nuisance to the people of America.

The close relationship between parasites and host is an example of symbiosis. It means living together. In some relationships, one organism benefits and the other is not affected. Fish called remoras live with huge sharks. Remoras get a free ride and food. This is called commensalism  A kind of plants called lichen have two parts in them- the fungi and the algae. Fungi provide support and water and the algae make food. Thus both are benefited. This is called mutualism

Questions

1.  Write a note on predators                             …. 1^st paragraph

2.  Write a note on parasites                              …. 2^nd paragraph

3. What are the difference between predators and parasites …. Short points of 1^st & 2^nd paragraphs

4. What is known as biological control            …. 3^rd paragraph

5. What is symbiosis                                          … 4^th paragraph

6. What is Commensalism                                   … 4^th paragraph

7. What is mutualism                                           …4^th paragaraph                                                                                                            

Drafted, printed and circulated among his students by K.J. Thomas, St.Thomas Academy, College Road, Ranni, dated 20^th January 2006.I wish all my students blessings of God Almighty and success in Exam and also in Life.