Chapter 19

Suggested answers to questions from the textbook

1. What is an adaptation?

Ans. An adaptation is a characteristic that helps an organism survive.This adaptation may be structural, functional or behavioural.

2. What is the difference between an ecosystem and a habitat?

Ans. The sea has many places where animals and plants live they are calledhabitats. Ecosystems are a combination of habitats and can be as small asthe space under a rock or as large as a barrier reef.

3. Give three examples of structural adaptations.

Ans. Spines, armour, interlocking vertebrae

4. How does a swim bladder help a fish survive?

Ans. Since density increases with depth, fish mostly live at a depthwhere their density equals that of the surrounding water. Some fish haveair or swim bladders (Figure 200.1) which they use to change the amountof air in their bodies and so change their density. This allows them tolive at different depths in the ocean.

5. Why do some animals live in schools?

Ans. For protection. Fish can swim together in schools to look like onelarge fish

6. How can territorial behaviour help a species survive?

Ans. Territorial behaviour can reduce fighting and competition for resources.

Territorial behaviour also helps to improve a species. Strong individualsget the best nesting or feeding sites and the weaker individuals may noteven attract a mate. This results in the weaker individuals with less desirablecharacteristics not passing on these characteristics to the next generation.This behaviour also maintains a population balance and helps make sure thepopulation does not outstrip its resources.

7. Why do some fish have to be streamlined?

Ans. Animals such as sharks that need to move rapidly through the waterneed to be streamlined. These fish have muscular bodies, a cylindrical shapeand use fins to give them added thrust through the water.

8. Would a filter feeder be well adapted to a muddy habitat? Give a reasonfor your answer.

Ans. No. It would become smothered with sediments.

9. Imagine you are a short rounded fish which could only move quicklyin short bursts. Name two habitats that would give you the best chance ofsurvival.

Ans. Reef crevice, rocky pool.

10. What is mutualism? Give an example of this type of relationship andindicate the effect of the relationship on each animal.

Ans. Mutualism is a close relationship between two organisms in whichboth benefit greatly from the association. This association is necessaryfor the organisms to survive.

A good example of mutualism is the relationship between algae and clams(discussed in Chapter 17). The green algae (zooxanthellae) lives insidethe shell of the clam and provides it with the oxygen and food the clamneeds to survive. In turn, the clam provides the algae with protection,carbon dioxide and nutrients (from its waste products).

11. Look at the food web on page 202. List the groups of animals actingas competitors. List some predator prey relationships.

Ans. Competitors - Heron, large fish, pelican, turtle.

Predator (Heron) Prey (Prawns) etc,

12. Give one similarity and one difference between a parasitic and apredator prey relationship.

Ans. Similarity - Feeds of organism

Difference - Parasites have a host - they stay with the organism

13. Give three examples of how an animal's behaviour can help it survive.

Ans. Avoid predators, improve chances of attracting a mate, protect itselffrom the elements.

14. Explain the unique relationship between the goby and the shrimp.

Ans. Some different species live together and share the same shelter.Both animals generally benefit from this association. An example of thisis the goby fish which lives in the burrow of the pistol shrimp (Figure.2). The pistol shrimp builds the burrow but has poor eyesight. The gobyacts as a sentry, warning of imminent danger, as well as capturing foodwhich it shares with the shrimp.

15. What is the difference between commensalism and mutualism? Give oneexample of each.

Mutualism is a close relationship between two organisms in which bothbenefit greatly from the association. This association is necessary forthe organisms to survive.

Commensalism is a loose relationship that exists between two differentorganisms and which is beneficial to one or both, but is not necessary fortheir actual survival. However, animals with this relationship have a betterchance of surviving their environment.

Commensalism comes in varying degrees. In most cases, one half of therelationship benefits from the relationship and the other is not affectedeither way, for example, where the organisms eat the same food without actuallycompeting. A good example of commensalism is the relationship between theremora and the shark (see Chapter 18). The remora attaches itself to theshark's body with a sucker and is transported around (Figure .1). The remorais then handy to feed on the scraps from the shark's meals. When the sharkstops feeding, the remora detaches itself and searches for its own food.It may attach itself to another shark later. The shark merely toleratesthe presence of the remora.

16. How does territorial behaviour help to improve a species' chanceof survival?

Ans. Territorial behaviour also helps to improve a species. Strong individualsget the best nesting or feeding sites and the weaker individuals may noteven attract a mate. This results in the weaker individuals with less desirablecharacteristics not passing on these characteristics to the next generation.This behaviour also maintains a population balance and helps make sure thepopulation does not outstrip its resources.

Territorial fights that do take place may only be mock fights designedto establish physical supremacy. However, other animals, such as the fishcalled the mangrove Jack, will fiercely attack intruders. This fish caneven be caught with lures pulled through its territory rather than thoseoffering food.

Chapter 19

Suggested answers to questions from the textbook

Suggested answers to diving deeper questions