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Unit 8.13 ReproductionOverview of the unit

In this unit, students will first learn about asexualreproduction, with reference to Euglena and yeast.They then investigate the structure of a floweringplant as an example of sexual reproduction. Theycompare asexual and sexual reproduction, and moveon to study natural selection and selective breeding.Finally they choose one example of selective breedingto research in detail and present their findings to therest of the class.

Concept strands

In completing this unit students will work towardsLearning outcomes L6, L7 and L8.

Learning

outcome

Emerging Developing Mastered

L6 Compare

sexual and

asexual

reproduction.

Identify

examples

of sexual

and asexual

reproduction.

Describe

examples

of sexual

and asexual

reproduction.

Compare sexual

and asexual

reproduction.

L7 Explain

examples

of natural

selection.

Outline

the process

of natural

selection.

Describe

the process

of natural

selection.

Explain examples

of natural

selection.

L8 Describe

the

advantages

anddisadvantages

of selective

breeding.

Identify

examples

of selective

breeding.

Describe

the process

of selective

breeding.

Describe the

advantages and

disadvantages of

selective breeding.

Investigating scientifically strands

The work in this unit will allow students to practiceand improve the following process skills:

Investigative

skills

Emerging Developing Mastered

S11 Draw a

conclusion,

consistent

with the data,

and explain it

using scientific

knowledge and

understanding.

Draw a

conclusion.

Draw a

conclusion,

related

to the

scientific

question or

prediction .

Draw a

conclusion,

consistent

with the data,

and explain it

using scientific

knowledge and

understanding .

Equipment and resources required

flower, scalpel, tweezers, magnifying glass, tile, glue,scissors

Key terms

adapt – changes in an organism’s characteristicsover time; the species adapts to have characteristicsuseful in its environment

antibiotics – medicines that kill bacteria; they areuseful for some infectious diseases, and to controlinfection after injuries or medical operations

asexual reproduction – this is reproduction withonly one parent organism

bud – a bud is a small growth that will becomesomething new; on a tree, a bud will become a newbranch or a flower

camouflage – colors or markings that cannot easily

be seen against the environment; soldiers wear greenand black to camouflage themselves in forests, andyellow and brown in deserts

characteristic – something about an organismor other thing; for example, ‘having black hair’ or‘having light green leaves’ is a characteristic

drug resistance – when a drug does not work to killan organism that causes disease; this is because theorganism has changed

electron microscope – a microscope that uses abeam of electrons instead of light; it shows details at

a much higher magnification than a normal opticalmicroscope

embryo – the bundle of cells that will be a newmulticellular organism

extinct – when all organisms in a species are dead

fertilization – this happens when the male andfemale gametes (sperm and ovum) meet and join; wesay that the ovum is fertilized

fission – when a cell reproduces by splitting into twoidentical copies

fragmentation – one part of a multicellular

organism breaks off and grows into a new individualfusion – when the male and female gametes join;the two cells become one

gamete – a cell needed to make a new organismduring sexual reproduction

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individual – a single organism; for example, youare an individual human

inherit – when an organism has a characteristicthat is the same as a characteristic from one or bothparents

mate – the mate of a female fish is a male fish

medical operation – cutting open a human bodyto treat an illness (for example, to remove cancer orto fix the heart)

misuse – using something wrongly, or for the wrongpurpose

multicellular organism – an organism with morethan one cell

natural selection – the process in which organismswith useful characteristics survive and reproduce;natural selection ‘chooses’ useful characteristics overtime

nectar – a sweet liquid produced by some flowers;bees and other insects drink nectar

offspring – the new organism or organisms; forexample, the offspring of birds are baby birds

organ – part of an organism with a particularfunction or functions

ovum or egg – the gamete provided by a femaleorganism (if there is more than one egg, we say ‘ova’)

pollen – a sticky powder found in flowers; bees andother animals move pollen from flower to flower

population – all the individuals of a species (we cantalk about the total population, or the population ofan area; for example, the human population of theworld is 7 billion; the population of Abu Dhabi is2.2 million)

reproduce – when an organism or organisms makenew organisms of the same species

resistant – not affected by something very much;resistant bacteria are not killed by antibiotics

rise – when yeast produces bubbles of carbondioxide and makes the bread mixture increase in size

selective breeding – when humans choose whichindividual plants or animals will be the parents forsexual reproduction

species – a type of organism (for example, lions area species of mammal; kestrels are a species of bird;date palms are a species of plant)

sperm – the gamete provided by a male organism

variation – a measure of the different characteristicsfound among different individual organisms in aspecies

vegetative reproduction – small copies of theorganism grow as part of the original organism; theythen drop off and live as new individuals

zygote – the fertilized egg; it is a single cell withproperties of the sperm’s nucleus and the egg’snucleus

Common misconceptions• Sexual reproduction only happens in

animals.• Asexual reproduction only happens in

microorganisms.• Eggs and seeds are non-living.

Team, individual and class activitiesGetting started

In units 7.8 and 7.12, students were introduced tothe idea of variation. They considered the causes ofvariation and how different organisms have featuresthat help them survive. This introductory sectionserves as a brief revision by looking at the features ofa typical predator and prey (a kestrel and a mouse).

1 Reproduction

Students should recall that all living things reproduce(it is one of the letter Rs in MRS GREN – see Unit

6.13). This first section looks at reproduction bysingle-celled organisms using Euglena and yeast asexamples.

A single Euglena has one nucleus.

Activity 1.1

There are several videos showing Euglenafission, for example https://www.youtube.com/watch?v=Y_2NDmlBEwU

Explain to students that when just one parent cellis involved (as with Euglena and yeast) the processis called asexual reproduction. It may be worthpointing out at this stage that ‘a-’ in front of a wordmeans ‘not’. For example, asymmetric means ‘notsymmetric’.

Emphasise that with asexual reproduction, thedaughter cells are copies of the parent cell, so thereis little variation within a population. Ask Why

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might the lack of variation be a problem? Lead studentsto the idea that in a changing environment mostorganisms might die but, if variation exists, one ortwo might have features enabling them to survive.

Worksheet 13.1 (page 184) provides a set ofinstructions for propagating African violets, with

questions to consolidate ideas about asexualreproduction.

2 Sexual reproduction

Sexual reproduction occurs when there are twoparents. It occurs not only in animals but also inflowering plants. Flowering plants cannot move fromone place to another, so they have other strategiesthat allow male and female gametes to meet. One ofthese is pollination by insects.

Activity 2.1

Each team will need: flower, scalpel, tweezers,magnifying glass, tile

Suitable flowers for this practical are tulips, or anyother flower with male and female organs.

Students look carefully at the flower and identifythe features they can see on the diagram beforeremoving the sepals and petals.

Which parts of the flower make up the stamen?(Answer: the anther and filament)

Which parts of the flower make up the pistil?(Answer: the stigma, style and ovary)

Find the name of the part where you can see pollen.(Answer: the anther)

Once students have sliced the pistil, they shouldobserve the ovary and ovules.

The male gamete is in the pollen, and duringfertilization, this male gamete unites with the femalegamete inside the ovule.

Unlike in asexual reproduction, this time twodifferent cells are joining to make a completelydifferent cell to either of the parent cells – the newcell (the zygote) is not an exact copy of either parent.

Students will revisit this in part 4 of this unit.Worksheet 13.2 (page 187) is a cut and stick exerciseto consolidate students’ understanding of sexualreproduction in a flowering plant.

3 Natural selection

The concept of natural selection is covered in thissection with reference to three examples: the finches

on the Galapagos Islands, peppered moths and thedodo. It can be explored further using Worksheet13.3 (page 189).

4 Comparing asexual and sexual reproduction

Activity 4.1

Answers:

Asexual reproduction

Advantages:

Reproduction is fairly fast

Less energy is needed to reproduce

There is no need to find a mate

Useful characteristics will definitely be passed on tothe new organism

Disadvantages:

If one organism cannot fight off a disease, this willbe true for all the organisms

If the environment changes, the organism cannotadapt quickly

Sexual reproduction

Advantages:

Variation means the organism can adapt over a fewgenerations to adapt to a changing environment

Variation helps defend the population againstdisease

Disadvantages:

The process of reproduction takes time and energy

A male and a female need to be in the same place tomeet

Worksheet 13.4 (page 192) is a True or False exercisesummarizing differences in asexual and sexualreproduction.

5 Selective breeding

The concept of selective breeding is covered in thissection with reference to breeding of crops and dogs.The problem of drug resistance is also considered inthis section.

Worksheet 13.5 (page 194) is a loop game that testsstudents’ comprehension of this unit. Cut out andshuffle the cards, then hand out a set to each team.Their task is to put the chain of cards in order.

6 Presentation task

Each team will prepare a talk or PowerPointpresentation on one aspect of selective breeding.

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Differentiation

Worksheets 13.1, 13.3 and 13.5 are most suitable forExtension students.

Worksheets 13.2, 13.4 and 13.5 are most suitable forSupport students.

Assessment

Making use of peer assessment

Ask students within teams to test each other on thekey terms from this unit.

Collecting items for evidence of achievement

Completed worksheets and presentations

Success criteria for the learning outcomes

Students will be able to:

L6: Compare sexual and asexual reproduction.• Emerging: Identify examples of sexual and

asexual reproduction.• Developing: Describe examples of sexual

and asexual reproduction.• Mastered: Compare sexual and asexual

reproduction.

L7: Explain examples of natural selection.• Emerging: Outline the process of natural

selection.• Developing: Describe the process of natural

selection.• Mastered: Explain examples of natural

selection.

L8: Describe the advantages and disadvantages ofselective breeding.

• Emerging: Identify examples of selectivebreeding.

• Developing: Describe the process of selectivebreeding.

• Mastered: Describe the advantages anddisadvantages of selective breeding.

Encouraging self-reflection and self-assessment instudents

Set students this task: From this unit, write down:• one thing that surprised you• three things you will try to remember • five new words you have learned.

Further suggestions for additional activitiesand investigations

See Worksheet 13.1 – students could set up thisactivity in the classroom or at home.

Links, references, URLs for the students to use

A short video clip about asexual reproduction:

http://www.bbc.co.uk/nature/adaptations/Asexual_reproduction#p00htlt4

An interactive quiz about evolution and naturalselection:

http://www.bbc.co.uk/schools/gcsebitesize/science/ edexcel/classifcation_inheritance/evolutionact.shtml

A game about natural selection:http://phet.colorado.edu/en/simulation/natural-selection

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