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Variation and the Role of Reproduction

In this worksheet, students study the variation within species and between organisms, caused mainly by the way characteristics that are passed on from generation to generation through genes.

'Variation and the Role of Reproduction' worksheet

Key stage:  KS 4

Curriculum topic:  Biology: Evolution, Inheritance and Variation

Curriculum subtopic:  Genetic Variation in Species

Difficulty level:  

down

Worksheet Overview

QUESTION 1 of 10

Individuals within a species show variation. This means that individuals look different from one another. Think about the students in your class. Do they all look the same? No! There are differences in eye, hair and skin colour, differences in the shape of facial features, bone structure and many more differences, which may not even be visible. We say that individuals have different characteristics

 

How do these differences come about? A lot of our characteristics are inherited. That means we get them from our parents through their DNA. Those characteristics are coded for by bits of DNA called genes and they are passed to us by reproduction.

 

All organisms reproduce, but in different ways. Reproduction ensures that the species will survive and instinctively all organisms want to survive through time. There is sexual and asexual reproduction. Sexual reproduction involves two parents and asexual only one. Commonly, all complicated organisms reproduce sexually. 

 

In order to understand sexual reproduction you have to know that DNA is kept in the nucleus of cells in the form of chromosomes. Humans have 46 chromosomes arranged in 23 pairs. Genes make some parts of the chromosomes. One chromosome from each pair of the mother's chromosomes are passed to the offspring (the child) and the same happens with the father's chromosomes. In effect, half of each parent's DNA passes to the offspring. There is a pair of chromosomes called the sex chromosomes and these determine the sex of the offspring. The female sex chromosomes are XX and the male XY.

However, environmental factors play a big role in shaping our characteristics, too.

 

Let's explore more about variation and reproduction in the questions.

The cats in the picture are all of the same breed. However, they have different fur colours and patterns and even eye colour. Do you know any other breeds of cats that look different to these guys?

 

What do we call the fact that organisms differ to each other?

Write one word.

Look at the picture of this family:

 

 

Can you see a resemblance between the parents and the children? Notice how similar the boy looks to his father. How did the boy inherit his father's wavy hair and colour?

Write one word.

The little girl has beautiful natural red hair. However, the lady's red hair is not natural but coloured. What do we call variation that is not inherited?

accidental

colourful

atmospheric

environmental

What characteristics may this man pass to his children? Tick all that apply.

 

nose shape

hair colour

eye colour

big muscles

Identical twins have exactly the same DNA. Imagine that the two girls in the picture develop different eating habits when they grow up; for example, one may be a healthy eater, whereas the other one may eat food high in sugar and fat.

 

 

Which one will be more prone to heart disease?

none, because they have not inherited the heart disease gene from their parents

both, because one of their parents has heart disease

the one with the unhealthy eating habits is more likely to develop heart disease

Mutations are spontaneous changes in the DNA. For example, Radiation from the sun can cause a mutation in the DNA of a skin cell and this can start reproducing without control. What is the name of this condition?

mole

skin cancer

eczema

A woman is pregnant with twins and a full genetic test is being done on the foetuses (the unborn babies) to determine if they are predisposed to a disease. It was found both had inherited the Y chromosome. What is the sex of the foetuses?

female

male

Let's revise some KS 3 science. Human cells have 23 pairs of chromosomes in their nucleus. Sex cells carry one chromosome from each pair. What is another word for sex cells?

Write one word.

Microorganisms reproduce asexually because they are simple organisms, so only one parent can do the job. The diagram below shows the four stages of asexual reproduction in a unicellular (one cell) organism.  

 

 

What is essential to be done by the mother cell before the two daughter cells are produced?

the cell components need to be duplicated

the mother must prepare her daughters for their birth

the mother cell finds an appropriate environment to reproduce

Tick TWO statements that are true of asexual reproduction.

all offspring are identical

all offspring are clones of their mother

offspring can be of a different sex

asexually reproduced organisms show great variation

  • Question 1

The cats in the picture are all of the same breed. However, they have different fur colours and patterns and even eye colour. Do you know any other breeds of cats that look different to these guys?

 

What do we call the fact that organisms differ to each other?

Write one word.

CORRECT ANSWER
variation
EDDIE SAYS
Organisms of the same species are different to each other due to variation.
  • Question 2

Look at the picture of this family:

 

 

Can you see a resemblance between the parents and the children? Notice how similar the boy looks to his father. How did the boy inherit his father's wavy hair and colour?

Write one word.

CORRECT ANSWER
DNA
genes
genetics
EDDIE SAYS
Characteristics pass to children from their parents through DNA/genes.
  • Question 3

The little girl has beautiful natural red hair. However, the lady's red hair is not natural but coloured. What do we call variation that is not inherited?

CORRECT ANSWER
environmental
EDDIE SAYS
There is inherited and environmental variation. Colouring hair is an environmental characteristic as it actually changes the inherited one. The lady's natural hair may have been blonde, brown or even black.
  • Question 4

What characteristics may this man pass to his children? Tick all that apply.

 

CORRECT ANSWER
nose shape
hair colour
eye colour
EDDIE SAYS
It is possible that the man will pass all of these characteristics to his children, except for the muscles. He was not born with these muscles, but they developed through hard training. It is an environmental characteristic.
  • Question 5

Identical twins have exactly the same DNA. Imagine that the two girls in the picture develop different eating habits when they grow up; for example, one may be a healthy eater, whereas the other one may eat food high in sugar and fat.

 

 

Which one will be more prone to heart disease?

CORRECT ANSWER
the one with the unhealthy eating habits is more likely to develop heart disease
EDDIE SAYS
Eating habits are an environmental factor. Even if two people have identical DNA, like in the case of identical twins, lifestyle still plays a role in their overall health. The girl with the unhealthy lifestyle will be more likely to develop heart disease.
  • Question 6

Mutations are spontaneous changes in the DNA. For example, Radiation from the sun can cause a mutation in the DNA of a skin cell and this can start reproducing without control. What is the name of this condition?

CORRECT ANSWER
skin cancer
EDDIE SAYS
Skin cancer is caused when radiation from the sun causes a change in the DNA of a cell. That cell will then start reproducing abnormally, without being able to stop.
  • Question 7

A woman is pregnant with twins and a full genetic test is being done on the foetuses (the unborn babies) to determine if they are predisposed to a disease. It was found both had inherited the Y chromosome. What is the sex of the foetuses?

CORRECT ANSWER
male
EDDIE SAYS
The Y chromosome can only be inherited from the father because only men have it. If an unborn baby has inherited the Y chromosome, it will definitely be male.
  • Question 8

Let's revise some KS 3 science. Human cells have 23 pairs of chromosomes in their nucleus. Sex cells carry one chromosome from each pair. What is another word for sex cells?

Write one word.

CORRECT ANSWER
gamete
gametes
EDDIE SAYS
Sex cells are also called gametes.
  • Question 9

Microorganisms reproduce asexually because they are simple organisms, so only one parent can do the job. The diagram below shows the four stages of asexual reproduction in a unicellular (one cell) organism.  

 

 

What is essential to be done by the mother cell before the two daughter cells are produced?

CORRECT ANSWER
the cell components need to be duplicated
EDDIE SAYS
All components of the mother cell (e.g. cytoplasm and nucleus) must be duplicated, so that daughter cells can have one each.
  • Question 10

Tick TWO statements that are true of asexual reproduction.

CORRECT ANSWER
all offspring are identical
all offspring are clones of their mother
EDDIE SAYS
Asexual reproduction gives daughter cells that are identical (clones) of their mother cell.
---- OR ----

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