Variation Between Individuals in a Species Can Be Continuous Or Discontinuous, Inherited

The millions of types of living things can be organised into categories, where we group together organisms with similar features. This is called the classification system. Variation between individuals in a species can be continuous or discontinuous, inherited or environmental.

Species A species is a category within the classification system. Living things of the same type belong to the same species. For example, humans are one species and dogs are another species. Individuals of the same species can reproduce to make more individuals of the same species. Two individuals belonging to different species cannot normally reproduce together. If they do, their offspring is usually infertile and unable to reproduce. For example animals called ligers are produced when a male lion and a female tiger reproduce. But a liger cannot have offspring. This means that lions and tigers are different species.

What is variation? All people are human. They belong to the same species. Your friends and classmates may have different eye colour and hair colour. Some will be boys and some will be girls. Some will be tall and some will be shorter. The presence of differences between living things of the same species is called variation. Variation between different species is always greater than the variation within a species. Some of the features of the different organisms in a species show continuous variation, and some features show discontinuous variation.

Continuous variation: Human height is an example of continuous variation. Height ranges from that of the shortest person in the world to that of the tallest person. Any height is possible between these values. So it is continuous variation. For any species a characteristic that changes gradually over a range of values shows continuous variation. Examples of such characteristics are:  height  weight  foot length.

1 If you record the heights of a group of people and draw a graph of your results, it usually looks something like this:

The more people you measure, and the smaller the categories you use, the closer the results will be to the curved line. This shape of graph is typical of a feature with continuous variation. Weight and foot length would give graphs similar in shape to this. Discontinuous variation: Human blood group is an example of discontinuous variation. There are only 4 types of blood group. There are no other possibilities and there are no values in between. So this is discontinuous variation. A characteristic of any species with only a limited number of possible values shows discontinuous variation. Here are some examples:  gender (male or female)  blood group (A, B, AB or O)  eye colour.

2 Inherited and Environmental variations Some variation within a species is inherited, and some variation is due to the environment.

Inherited causes of variation: Variation in a characteristic that is a result of genetic inheritance from the parents is called inherited variation. Children usually look a little like their father, and a little like their mother, but they will not be identical to either of their parents. This is because they get half of their inherited features from each parent. Each egg cell and each sperm cell contains half of the genetic information needed for an individual. When these join at fertilisation a new cell is formed with all the genetic information needed for an individual. Here are some examples of inherited variation in humans:  eye colour  hair colour  skin colour  lobed or lobe-less ears. Gender is inherited variation too, because whether you are male or female is a result of the genes you inherited from your parents.

Environmental causes of variation: Characteristics of animal and plant species can be affected by factors such as climate, diet, accidents, culture and lifestyle. For example, if you eat too much you will become heavier, and if you eat too little you will become lighter. A plant in the shade of a big tree will will grow taller as it tries to reach more light. Variation caused by the surroundings is called environmental variation. Here are some other examples of features that show environmental variation:

 Your language and religion  Flower colour in hydrangeas - these plants produce blue flowers in acidic soil and pink flowers in alkaline soil.

3 Both types together Some features vary because of a mixture of inherited causes and environmental causes. For example, identical twins inherit exactly the same features from their parents. But if you take a pair of twins, and twin 'A' is given more to eat than twin 'B', twin 'A' is likely to end up heavier.

Natural and Artificial selections Natural selection: Within a population of animals, plants or any living organisms, there will be inherited variations. Within each species the individuals with the variations best suited to the environment will survive better than the others. More of them will survive to reproduce than the others. When they do, they pass on the genetic information for these variations to their offspring. Species gradually evolve in this way. This process is called natural selection. Over time a population can change so much it may even become a new species, unable to reproduce successfully with individuals of the original species.

Artificial selection: Artificial selection is when people use selective breeding to produce new varieties of a species. A variety is a type of a particular species that is different in some clear way from other varieties of that species. For example, pedigree dogs come in lots of different varieties, called breeds of dog. They may be different colours and sizes, but they are all still dogs. They are all still the same species. Different varieties of dog have been produced by selective breeding. Ex: Selective breeding of cows Suppose you wanted a variety of cow that produced a lot of milk. This is what you could do:  choose or select the cows in your herd that produce the most milk  let only these cows reproduce  select the offspring that produce the most milk  let only these offspring reproduce  keep repeating the process of selection and breeding until you achieve your goal.

4 Other examples of selective breeding The key here is to identify the feature you want, and only breed from the individuals that have that feature. Here are some examples of what selective breeding can produce:  hens that lay big eggs of a particular colour  cattle that produce lots of meat  tomato plants that produce lots of tomatoes  crops that are resistant to certain plant diseases.

Classification There are millions of species on our planet. It would be difficult if we just tried to describe and name each one individually. Although species can be very different from each other, many of them have similar features that allow us to put them into groups. Putting different species into different groups according to their features is called classification. Classification of animals: Animal Kingdom can be split up into main groups, vertebrates (with a backbone) and invertebrates (without a backbone).

I- Vertebrates 1- Fish  They are the largest group of vertebrates.  They come in many sizes and shapes.  Many fish have a moist skin covered with scales that protects them.  They have fins that help them to steer and balance in the water.  Their body temperatures vary in the water.  They breathe through gills.  They are cold blooded

2- Amphibians  Their body temperature varies with their surroundings.  Amphibians hatch from eggs and they can live on land as an adult.  Young amphibians breathe through gills like fish.  Adult amphibians breathe air from lungs.  Some have smooth moist skin.  Amphibians are able to live on land as well as in the water.

3- Reptiles  Reptiles can move at various speeds.  They lay their eggs on land.  They have dry scaly skin.  They can include animals as large as a crocodile.

5  Their body temperature varies with their environment.  They live in hot, dry deserts and in warm, wet tropical rain forests.

4- Birds  Birds lay hard shelled eggs that hatch in their nest.  There are about 9,000 types of birds.  Birds are vertebrates that have wings and they are covered with feathers. No other animal has this feature.  The bird’s skeleton is very light in weight. This helps them to fly.  Birds range in size from as small as your finger or as large as a human.  Birds are warm-blooded

5- Mammals  They include a wide range of animals: ape, lions, kangaroos, bats, and etc.  Their young grow inside the mother.  Humans are mammals but they (animals) have more hair than we do.  The hair keeps the animals warm.  They feed milk to their young

6 II- Invertebrates:

1- Sponges  They look like plants but they are animals.  Sponges stay fixed in one place.  Their bodies are full of holes and their skeleton is made of spiky fibers.  Water flows through the holes of their body which enables them to catch food.

2- Corals, hydras and jellyfish  Corals look like plants but they belong to the animal kingdom.  They have soft tube-like bodies with a single opening surrounded by arm-like parts called tentacles.  They feed by catching tiny animals in their tentacles.  Hydras have tentacles that catch their food.  They move from place to place.  Hydras are much smaller animals.  Jellyfish catch shrimp, fish, and other animals in its tentacles also.

3- Flatworms  They have a head and a tail, and flattened bodies.  A tapeworm is a flatworm that can live inside the body of animals and humans. It can cause you to become sick

4- True worms  They have rounded bodies.  They live in damp places and they can also live inside humans and other animals.  They can make people and other animals sick.  Their bodies are divided in segments, or sections.  They prefer burrowing through moist soil.  This allows them to move easily and it keeps them from drying out.

5- Arthropods  Arthropods are a group of invertebrates with jointed legs and hard exoskeleton that protect the arthropod.  As it grows, it molts, or sheds its old exoskeleton.  Then it grows a new exoskeleton that allows its body to continue to grow.  A lobster is an arthropod.  The largest group of arthropods is insects

7 The diagrams below show four different groups of animals.

a) These animals belong to four different groups of animals. Here is a description of each group. A. The animals in this group have a hard outer covering and eight jointed legs. Which animal belongs to group A? ______B. The animals in this group have a tough spiny skin and most of them are star shaped. Which animal belongs to group A? ______C. The animals in this group have a body that is divided up into a series of parts or segments. Which animal belongs to group A? ______D. The animals in this group have a soft body and are usually protected by a shell. Which animal belongs to group A? ______b) Here is a diagram of a fish.

Write down a description of a fish. Use the diagram and any knowledge you already have of their structure to help you. You should give it at least three features that are typical of most fish.

______

8 Describe, in as much detail as you can, the 5 different vertebrate groups. Give 2 examples of animals from each of these groups.

Group 1 ______Examples of animals: ______and ______

9 1. In the sentences below, draw a ring around the word that best describes you.  I have black/ blue/ brown/ grey/ green/ hazel eyes.  I have black/ dark brown/ light brown/ blonde hair.  I have straight/ wavy/ curly hair. We call features such as eye colour characteristics.

2. Look at the pictures of different breeds of dogs. Then complete this table by putting a tick in the correct boxes: Characteristic Terrier Basset hound Labrador Long Legs: short Long Tail: short Hang down Ears: Stick up

3. Write down the breed of dog that has short hair, long legs, and ears that hang down. ______

4. Complete the sentences: a) Dogs can ______with each other and produce ______. b) So they belong to the same ______. c) Members of the same species are ______in some ways. But they are different in others. d) We say that they ______.

10 1. Complete the sentences: a) Many members of the royal Habsburg family had a characteristic called the ______. b) This characteristic is seen in different ______. c) So we say that the characteristic is ______. d) This means that the characteristic is passed on from ______to ______.

A family tree shows:  How people are related to each other;  How a characteristic passes from parents to children.

2. Look at the family tree on page 40. Then complete the sentences. a) The number of generations in this family tree is ______. b) Paul has ______like his father and ______like his mother. c) Another inherited characteristic in this family tree is ______.

3. Use only the information on pages 41 and 42 to help you to complete the table. Tick the correct boxes. The first one has been done for you. Characteristic Inherited Environmental Both Height in peas √ Size of leeks Hair colour of twins Height of twins Skin colour of twins Scar on one twin Eye colour of twins

11 1. Explain why a family tree is useful when deciding if a characteristic is inherited.

The picture below is of a family tree, which shows how a very clear characteristic has been passed on.

2. Describe the characteristic that is inherited in this family.

3. How many generations are shown in this family? 4. Who did K inherit his blaze from?

5. Are inherited characteristics like the blaze always passed on to children? Explain your answer.

6. Is a white streak in the hair always an inherited characteristic, especially nowadays? Explain your answer.

12 Describing living things

1. Humans and gorillas are two different species of animals. Complete the following table about these two species. Differences between humans and gorillas Characteristic Human Gorilla How it walks Feet Hair

2. Read the poem on page 43. Write down three animals that Nick could be. ______

3. Read the description on page 43. What is Nick? ______

4. Match the words with their descriptions. Abdomen The part that makes silken threads Spinneret The hard outer body parts Exoskeleton An animal that kills and eats other animals Carnivore The tail end of the body

5. Two ways that hoverflies and wasps are similar are: ______

6. Two ways that hoverflies and wasps are different are: ______

13 Compare and contrast

Sometimes questions ask you to compare and contrast two things.

Remember:  When you compare, you look for characteristics that are the same or similar.  When you contrast, you look for differences.

Look at the pictures and then answer the questions.

1. Read the sentences below. a. Some of the sentences compare the spider and the hoverfly. Underline these in blue. b. Some of the sentences contrast the two animals. Underline these in red.  The bodies of the spider and the hoverfly are divided into parts.  The body of the spider has two main parts, but the body of the hoverfly has three.  The spider and the hoverfly have jointed legs.  The spider has eight legs, but the hoverfly has six legs.  The hoverfly’s abdomen is striped, but the spider’s is not. 2. Write down: a. One more similarity; b. One more difference between the spider and the hoverfly.

14 Describing what it is

The picture below shows a group of woodlice. All the woodlice in the picture belong to the same species.

1. Write down two variations that you can see between the animals in the picture.

2. Size is not an inherited variation in this species. Write down two possible reasons for the difference in size of these woodlice.

The picture below shows two different species of woodlice.

3. Write down three differences between species 1 and species 2.

15 The type of fingerprint you have

There are three main types of human fingerprint. They are shown below.

You can make a fingerprint using fingerprint ink on white paper. Or you can use talc and dark paper as follows: i. Cut a small strip of Sellotape; ii. Put it on the desk with the sticky side facing upwards; iii. Dip your finger into talc; iv. Put the flat of your finger onto the Sellotape; v. Peel off the Sellotape and stick it onto a piece of dark paper.

1. Look carefully at your fingerprint and then at the picture at the top of this page. Which type of fingerprint in the picture best matches yours?

2. Is your fingerprint a loop, does it point left or right?

3. Has your print got a single or a double core?

4. Find out and write down which is the commonest type of fingerprint in your class?

16 Sorting animals

1. On page 45, the animals are sorted into three groups. What are these groups? ______

2. Now sort the same animals into three different groups.

3. Write down one more way to sort these animals into different groups. ______

4. Of the two ways of grouping the animals that you have suggested, which do you think is the best? Why? ______

17 Classifying

1. Complete the following sentences: a) There are ______of different species of plants and animals. b) We can’t ______about every one of them. c) So we sort them into groups with lots of ______in common. d) We say that we ______them.

2. An eagle is a bird. So three things that I know about an eagle are: a) ______; b) ______; c) ______.

3. Birds, bats and dragonflies can all fly. But we put them into different groups because their other characteristics are different.

Write down one difference between:

1. Birds and bats; ______

2. Birds and dragonflies; ______

18 Classifying

1. Look at these two sentences and cross out the word in brackets that is wrong. a) Vertebrates are animals (with/ without) a backbone. b) Invertebrates are animals (with/ without) a backbone.

2. Look carefully at the two animals named in the table below. a) Are they vertebrates or invertebrates? b) What kind of hard body parts does each of them have? (Cross out the word or words in the brackets that are wrong.)

Name of animal Hard body parts

Crab (shell/ jointed skeleton)

snail (shell/ jointed skeleton)

3. Look at the pictures of skeletons on picture 48. a) They are made of ______. b) Both skeletons have: i. ______; ii. ______; iii. ______.

4. Complete the following diagram:

19 1. Complete this table

Invertebrate Name Segmented Hard body parts Legs group Jellyfish

Molluscs

Flatworms

True worms

Arthropods

2. Choose a picture of animal from page 50 or 51. Write a few sentences about that animal. ______