Higher Biology

AdaptationPart 1

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Adaptation 1

By the end of this lesson you should be able to:

Understand osmoregulation in freshwater andsaltwater fish. Know the differences between them in terms of number and size of glomeruli, filtration rate and chloridesecretory cells. Know how the salmon copes with 2 different environments.

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Introduction

An adaptation is a characteristic possessed by an organism which gives it an advantage in a particular environment.

Many adaptations have evolved over a very long period and have been selected for, to enable the organism to survive.

There are three categories of adaptations:

structural physiological behavioural

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Introduction

Over the next few lessons you are going to be studying the following adaptations:

Freshwater fish Saltwater fish Migratory fish Desert mammals Plants that live in deserts Plants that live in water

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Osmoregulation

Osmoregulation is the process of controlling the water and ion (salt) balance of the body.

In humans: The organs of osmoregulation are the

kidneys The hormone involved is called ADH- Anti

Diuretic Hormone. Insert and complete “The Kidney” revision

sheet from your pack into your notes.

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Osmoregulation

Can you remember the following terms?1. Isotonic2. Hypertonic3. Hypotonic4. Osmosis

What problems will fish that live in freshwater face?

What problems will fish that live in saltwater face?

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Freshwater bony fish

Live in………conditions

Water tends to the fish by osmosis.

So the fish has to get rid of excess water, but at the same time, not lose essential salt ions.

Hypotonic/hypertonic/isotonic

enter/leave

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Freshwater fish

How do they do it?

1. They do not drink2. They have many, large glomeruli

highfiltration rate of substances from the blood.

3. This produces a large volume of dilute urine (containing ammonia)

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Freshwater fish

How do they do it?4. The nephrons are very efficient at

reabsorbing salts from the filtrate back into the blood.

5. Their gills contain cells called chloride secretory cells which actively take up sodium and chloride ions into their blood from the water they live in.

Complete the “Freshwater fish” diagram from your diagram pack.

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Saltwater bony fish

Live in………conditions

Water tends to the fish by osmosis.

So the fish is constantly losing water through their gills and gut membranes.

Hypotonic/hypertonic/isotonic

enter/leave

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Saltwater fish

How do they do it?

1. They drink sea water to replace lost water

2. They have few, small glomeruli lowfiltration rate of water from the blood.

3. This produces a small volume of urine containing a non-toxic nitrogenous waste.

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Saltwater fish

How do they do it?4. Their gills contain cells called chloride

secretory cells which actively excrete sodium and chloride ions (gained by drinking sea water) out of their blood and into the water they live in.

Complete the “Saltwater fish” diagram from your diagram pack.

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Migratory fish

These migrate between fresh and salt water so have the problems of both freshwater and salt water fish!

How do they do it? You find out!

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Migratory fish

Use Torrance pages 169-170 to find out:What changes occur in the salmon when it

moves from fresh water into sea water and vice versa in terms of:

1. Hormones2. Filtration rate3. Chloride secretory cells

NB the eel faces the same problems!

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Practice Questions

Torrance1. TYK page 171 Q1-3

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Adaptation 1

Can you do it?

Understand osmoregulation in freshwater andsaltwater fish. Know the differences between them in terms of number and size of glomeruli, filtration rate and chloridesecretory cells. Know how the salmon copes with 2 different environments.