Ch 5. Symbiosis

Question 1

What is Symbiosis?

Answer 1

An ecological relationship between organisms of two different species that live in direct contact with one another. Theses are intimate relationships that have co-evolved over millions of years.

Question 2

Name the two types of symbiosis.

Answer 2

1. Mutualism

2. Parasitism

Question 3

What is Parasitism?

Answer 3

A relationship where one species benefits at the expense of the other.

Question 4

How does Parasitism occur?

Answer 4

The parasite derives its nutrition from another organism, the host, which it exploits.

Question 5

How is the host affected during/after parasitism?

Answer 5

The host is always exploited to some degree.

It can be harmed, or at least lose some energy/materials to the parasite.

Sometimes the hosts health is impaired slowly, allowing the parasite to exploit its host over a longer period of time.

Question 6

Why can’t parasites survive well outside of the hosts body?

Give an example of this.

Answer 6

Because of their limited metabolism.

e.g. Tapeworms do not have a digestive system since the host has already digested the food.

Question 7

What is an endoparasite?

Answer 7

A parasite which lives inside the host.

Question 8

What is an ectoparasite?

Answer 8

A parasite which lives outside the host.

Question 9

Give three examples of parasites.

Answer 9

1. Fleas
2. Ticks
3. Tapeworms

Question 10

Name three ways in which parasites can be transmitted to their host.

Answer 10

1. Direct Contact
2. Resistant Stages
3. Use of a Vector

Question 11

What is direct contact?

Give an example.

Answer 11

When the parasite is transmitted from person to person by physical contact e.g. head lice.

Question 12

What are Resistant stages?

Answer 12

A part of the parasite’s life cycle where they are resistant to adverse environmental conditions and can survive for long periods of time, until they come into contact with a new host.

Question 13

Give an example of a parasite which uses Resistant stages to pass from host to host and describe how this occurs.

Answer 13

The human tapeworm (which can be contracted from pork).

1. The pig becomes infected by ingesting tapeworm eggs.
2. Once inside the intestine, the eggs release the first stage larvae.
3. These then migrate to the muscles, where it develops into a cyst-like structure.
4. The cyst can survive for several years in the tissue of the pig (this is the resistant stage).
5. When humans become infected by tapeworms they can suffer from symptoms such as stomach pains, vomiting and weight loss.

Question 14

What is a vector?

Answer 14

A vector is a carrier which allows a parasite to pass from one host to another.

Question 15

Give an example of a vector.

Answer 15

The mosquito - carries the Plasmodium protoza (causes malaria) from human to human.

Question 16

What is a direct life cycle in parasitism?

Answer 16

When eggs are shed and pass onto a new member of the host species e.g. cat flea.

Question 17

What is an indirect life cycle in parasitism?

Answer 17

When a parasite uses both a secondary host species and a primary host species.

Question 18

What is the benefit of an indirect life cycle to a parasite?

Answer 18

Because it increases the chance of its offspring being transmitted to the primary host and many parasites can increase their numbers inside the secondary host by asexual reproduction.

Question 19

What kind of reproduction is carried out by parasites in their secondary host?

Answer 19

Asexual reproduction

Question 20

What kind of reproduction is carried out by parasites in their primary host?

Answer 20

Sexual reproduction

Question 21

Describe the stages of an Indirect life cycle of a tapeworm (parasite).

Answer 21

1. Tapeworm contaminates the grass
2. The cow eats the grass and so becomes infected with the tapeworm (secondary host).
3. The human eats the cow under cooked and the tapeworm is transmitted to the human (primary host).

*See Diagram in jotter for a better understanding.

Question 22

What is mutualism?

Answer 22

A relationship where both organisms involved benefit from the interaction.

Question 23

What are mutualistic relationships described as?

Answer 23

Interdependent. Becuase one cannot live with out the other.

Question 24

Describe three different types of Mutualism.

Answer 24

1. Relationships where both organisms provide a service e.g. Clown Fish and Anemones.
2. Relationships where one organism provides a service and the other receives a resource e.g. flowering plants and bees.
3. Relationships where both organisms receive a resource e.g. human gut microflora

Question 25

Describe the mutualistic behaviours of Cellulose-digesting protozoa/bacteria in the guts of herbivores.

Answer 25

Herbivores such as cows feed by grazing on plant matter and need to digest cellulose which makes up the cell wall of plant cells. However, many are not able to produce the cellulose-digesting enzyme cellulase.

Instead, they rely on micro-organisms (mainly bacteria or protozoa) in their gut to help digest their food. These cellulose digesting micro-organisms inhabit gut chambers such as the firs two chambers of a cow’s stomach.

The herbivore recieves sugar and other metabolites from cellulose breakdown, and the mico-organisms receive protection, warmth and a constant food supply.

Question 26

Describe the mutualistic relationship between photosynthetic algae and corals.

Answer 26

Coral polyps are sessile animals with a hard exoskeleton. They have a mutualistic relationship with zooanthellae (a unicellular algae tat live in and between its cells). The algae carry out photosynthesis to produce carbohydrates which the polyps us as an energy source and in return, the algae are provided with a sheltered place to live and a supply of nitrogen compounds from the polyps wastes, which can be used to make proteins.

Question 27

Describe the mutualistic relationship between Clown fish and anemones.

Answer 27

The anemones stings provide the fish with protection from predators and the fish defend the anemones from the butterflyfish that eat them.

Question 28

Describe the mutualistic relationship between Flowering plants and bees.

Answer 28

The bees pollinate the plants.

The plants provide nectar which is a food source for the bees.

Question 29

Describe the mutualistic relationship between Humans and microflora.

Answer 29

The human gut is full of many species of bacteria, fungi etc. which perform many useful functions such as:

1. fermenting unused energy substrates
2. training the immune system
3. preventing growth of pathogenic bacteria
4. regulating the development of the gut
5. producing vitamins such as boitin and vitamin K.

The microorganisms in return receive a steady supply of food.