Unit 3B

Question 1

Nitrogen

Answer 1

Used to make amino acids which are used to build protein.

All new cells are built of protein, so protein is essential for growth.

Question 2

Nitrate

Answer 2

The form in which nitrogen enters the plant, dissolved in soil water.

Soil water enters the root through root hair cells.

This is known as uptake or assimilation.

Question 3

Legumes

Answer 3

Plants such as peas, beans and clover.

They have bacteria living in their roots which are able to absorb nitrogen directly from the air into the roots.

Question 4

Animal proteins

Answer 4

Animals can only obtain protein by eating other organisms.

Herbivores eat plant protein, carnivores eat animal protein.

Protein moves along a food chain from one consumer to the next.

Question 5

Nitrogen cycle

Answer 5

A series of chemical reactions that allow nitrogen to be recycled through ecosystems.

Many of the steps are carried out by bacteria.

Question 6

Decomposers

Answer 6

Bacteria and fungi which break down dead material by feeding on it.

They release ammonia (which contains nitrogen) as a waste product.

Question 7

Nitrifying bacteria

Answer 7

Live in the soil.

Convert ammonia into nitrites and then into nitrates, which can be absorbed by plants.

Question 8

Denitrifying bacteria

Answer 8

Live in waterlogged soil.

Convert nitrates back into atmospheric nitrogen.

Question 9

Nitrogen fixing bacteria

Answer 9

Live in the soil or in the roots of legumes.

They convert atmospheric nitrogen into ammonia or nitrates.

Question 10

Essential plant minerals

Answer 10

Nitrogen (N), phosphorous (P) and potassium (K).

Question 11

Fertilisers

Answer 11

Used to replace nutrients lost in harvesting.

Used to improve crop yields, as crops grow better with fertiliser.

Question 12

Natural (organic) fertilisers

Answer 12

Waste materials produced by living organisms. eg. manure, straw, bird droppings (guano)

Advantages - good use of natural waste materials, improve and bind the soil

Disadvantages - release nutrients slowly, are bulky and hard to spread.

Question 13

Artificial (inorganic) fertilisers

Answer 13

Chemical fertilisers made in factories.

Different fertilisers have different combinations of minerals for specific uses - known as N:P:K ratios.

Advantages - easy to apply, nutrients released quickly and in specific quantities

Disadvantage - wash into rivers, expensive

Question 14

Overuse of fertilisers

Answer 14

Excess fertilisers can be washed off the land into rivers, lakes and the sea.

This results in algal blooms, which block the light for other plants and kill them.

As dead plants and algae are decomposed by bacteria, they use up the dissolved oxygen in the water.

This kills fish.

Question 15

Blue Flag Award

Answer 15

Introduced to combat beach pollution and habitat degradation.

Question 16

Problems caused by beach pollution

Answer 16

Illness due to bacteria in sewage

Loss of recreational areas due to litter and dirty water.

Reduction in biodiversity if wildlife are killed.

Loss of coastal habitats for young fish due to algal blooms.

Question 17

Evolution

Answer 17

Species change over time to become better adapted to their environment.

Question 18

Adaptation

Answer 18

Any feature that makes an individual better suited to their environment, and able to survive long enough to reproduce.

Well adapted species survive.

Less well adapted species become extinct.

Adaptations can be structural, physiological or behavioural.

Question 19

Structural adaptations

Answer 19

Describe how the body of an organism is suited to its environment.

This affects what it looks like.

eg. polar bears have thick fur and a fat layer for warmth, their fur is white for camouflage, they have small ears to reduce heat loss.
eg. cacti have leaves reduced to spines to deter grazers and reduce water loss, they have succulent stems to store water.

Question 20

Physiological adaptations

Answer 20

An adaptation to the internal processes of a plant or animal.

eg. clover produces hydrogen cyanide in its leaves to stop herbivores eating them.
eg. emperor penguins can store large quantities of oxygen in their blood, allowing them to dive for 22 minutes to hunt.

Question 21

Behavioural adaptations

Answer 21

Affect the way that an animal behaves, increasing its chance of survival.

Can be innate (inherited) or learned.

eg. grass snakes ‘play dead’, bees do a waggle dance to communicate.

Question 22

Desert mammals

Answer 22

Live in harsh conditions and use all 3 strategies to survive.

eg. kangaroo rats are camouflaged against the sand, never drink and hide in underground burrows to avoid the sun.

Question 23

Innate behaviour

Answer 23

Inherited behaviour which is genetically determined.

eg. newly hatched turtles head towards the sea, bees carry out a waggle dance and swarming behaviour.

Can be studied in woodlice using a choice chamber.

Question 24

Learned behaviour

Answer 24

Not carried out by all members of a species - only those with experience.

Helps organisms to survive.

Question 25

Stimulus

Answer 25

Triggers a response in an organism.

Can be internal (hunger, thirst) or external (temperature, day length).

Question 26

Habituation

Answer 26

An animal learns to stop responding to a repeated harmless stimulus.

eg. snails withdraw into their shells to avoid predators, but stop doing it with repeated tapping.

This saves energy and allows them to continue feeding.

Question 27

Imprinting

Answer 27

Newly hatched ducks and geese follow their mother towards water and food, and away from predators, which helps them to survive.

It is learned behaviour - they learn to follow the 1st large moving object they see (even human foster parents)

Question 28

Associative learning

Answer 28

Bees can be trained to associate colour with food, which helps them to survive.

If sugar solution is only placed on blue circles in an experiment, the bee will learn to associate the colour blue with food.

Question 29

Migration

Answer 29

Animals migrate long distances to find food and avoid harsh conditions. eg. whales, swallows

It is both innate and learned.

Birds instinctively fly in the correct direction, but learn the route as they get older.

Question 30

Group social behaviour

Answer 30

Many animals live in social groups to help them to survive.

eg. orcas, monkeys and many species of bird.

They hunt for food together, watch for predators and stay together for protection - safety in numbers.