Reproduction in Animals and Plants: a full term of science

Ten ready-to-teach lessons for Year 9 Biological sciences. Print this pack and the term is prepared: every lesson comes with a step-by-step plan, the questions to ask, a student worksheet, cut-out cards, a record sheet or exit tickets, an assessment kit and worked answers.

Start here: five minutes to Monday

1. Skim the term at a glance on the next page.
2. Print the lesson you need. Each lesson is three A4 sheets: plan, worksheet, and cards, a record sheet or tickets.
3. Gather the few items under “You need” on the plan. Most come from the science prep room, a florist or the supermarket.
4. Open the free interactive unit on your board or projector. Every plan tells you which picture to show and when.
5. Teach straight from the plan. Timings, talk prompts, misconceptions and worked answers are all on the one page.

For any Year 9 science teacher

The pack suits a biology specialist and a teacher working outside their own subject alike: each plan explains the idea in plain words, lists the misconceptions students bring, and gives worked answers. The big idea of the term: a species lasts only if its members make the next generation. Sexual reproduction joins two gametes, a small mobile male cell and a large food-filled female cell, made in organs whose form suits their job; the offspring vary, and variation helps some of them survive change. Asexual reproduction copies one parent quickly and needs no mate; the offspring are clones, which suits a stable place but leaves them all open to the same threat.

Two ways to run each lesson

Every lesson works as one 60-minute block, or as two 30-minute sessions; the split point is marked in every plan. Look ahead: Lesson 2 needs large flowers from a florist, Lesson 5 needs broad beans soaked overnight, and the Lesson 6 cuttings need about two weeks before the class checks them in Lesson 9.

Safety and care in one look

Wash hands after handling flowers, seeds and yeast; some plant sap and pollen irritate skin, so offer gloves, and lily pollen stains. Nothing in the science room is eaten, even the peas. The teacher does any cutting with a knife; students use blunt scissors. No bacteria are grown in class: Lesson 7 models them with numbers. Microscope slides and coverslips are handled by their edges.

The term at a glance

One lesson a week for a term. Each lesson stands on the ones before it, so run them in order where you can.

How the sequence builds

Lessons 1 to 3 meet the cells and organs of sexual reproduction: gametes and their form, the parts of a flower, and the journey of pollen. Lessons 4 and 5 follow fertilisation, inside and outside the body, and an ovule becoming a seed. Lessons 6 and 7 turn to asexual reproduction in plants, yeast and bacteria. Lesson 8 sets the two routes side by side, Lesson 9 tests what each means for survival when the world changes, and Lesson 10 brings it together.

Curriculum links (Australian Curriculum V9)

The whole term teaches the Science Understanding descriptor AC9S9U02 quoted on the cover. The lessons also work these Science Inquiry and Human Endeavour descriptors:

Assessment in this pack

• Every plan ends with “Answers and look-fors”: what meeting the idea sounds like in a Year 9 voice, with working.
• The assessment sheet near the front has a class observation checklist and a three-level rubric.
• Lesson 10 is the summative pair: the three living things task, plus the “Show what we know” check.

Materials for the whole term

One gathering session covers all ten lessons. Most of it comes from the science prep room, a florist and the supermarket. Three things are worth doing ahead: order large flowers for Lesson 2, soak the broad beans the night before Lesson 5, and set up the Lesson 6 cuttings at least ten days before Lesson 9.

The one-trip list

• From the prep room: hand lenses, microscopes, slides and coverslips, droppers, small beakers, blunt scissors, rulers and gloves.
• From a florist: large flowers with clear parts, such as lilies or alstroemerias, one for each pair.
• From the supermarket: fresh pea pods, dried broad beans, dried yeast, sugar and a bunch of mint with long stems.
• From the school grounds: a few flowers with bright petals and a few grass heads or she-oak sprigs.

Safety and care in one look

• Wash hands after handling flowers, seeds and yeast; offer gloves, as some sap and pollen irritate skin.
• The teacher does any cutting with a knife; students use blunt scissors.
• Nothing in the science room is eaten, even the peas and the beans.
• No bacteria are grown in class; slides and coverslips are held by their edges.

Assessment without extra work

The term assesses itself. Every lesson plan ends with worked answers and look-fors, and Lesson 10 is the summative pair: the task, in which students explain how three living things reproduce and how that helps them survive, and the final check. This sheet is the place to note what you see along the way.

The three levels

Class observation checklist

A tick a lesson is plenty; the Lesson 10 task and check fill the gaps.

Word wall cards

Cut out the cards and build the wall as the words arrive: gamete, sperm, egg, testes and ovaries in Lesson 1; stamen, anther, carpel and ovule in Lesson 2; pollination in Lesson 3; fertilisation, zygote, external and internal fertilisation in Lesson 4; seed and fruit in Lesson 5; asexual reproduction and clone in Lesson 6; budding and binary fission in Lesson 7; variation in Lesson 9.

Dear families

This term in science, Year 9 studies reproduction in animals and plants: the cells and organs that make new living things, and the two routes life takes to the next generation. Sexual reproduction joins two cells from two parents, so the young vary; asexual reproduction copies one parent, quickly and without a mate. Students analyse how each route helps a species survive.

Along the way your student will draw cells to scale, take a flower apart, look at pollen through a hand lens, open pea pods to count the ovules that became peas, grow new mint plants from cuttings, watch yeast cells budding, and model a disease sweeping through a field of identical banana plants.

Try this at home

• Open a pea pod or a bean pod. Count the seeds, and look for small flat ones that did not grow.
• Stand a cutting of mint, basil or a pot plant in a glass of water by a window, and watch for roots.
• Cut a fruit such as a capsicum or an apple across. Where are the seeds, and how many are there?
• On a walk, find a flower visited by insects or birds, and a grass with its flowers out in the wind. How do they differ?

What to ask your scientist

• Why is an egg cell so much bigger than a sperm cell?
• What is the difference between pollination and fertilisation?
• Why are all the bananas in a plantation clones, and why is that a risk?
• How does variation help a species survive?

A small note on care: students wash their hands after handling flowers, seeds and yeast, and nothing in the science room is eaten. No bacteria are grown in class.

Warm regards,

The Year 9 science team

Printed from the free seegongsik Reproduction in Animals and Plants teaching pack · seegongsik.com/au/y9/biological/AC9S9U02/pack

Small and mobile, large and stocked

A reproductive cell is called a gamete, and each one carries half the instructions for a new individual. Gametes come in two forms, built for two different jobs. The male gamete is small and mobile: an animal sperm has a tail to swim, a middle piece packed with mitochondria that release energy, and a tip with enzymes that break through the coat of the egg. The female gamete is large and stays where it is: an egg carries a store of food for the first days of growth. In flowering plants the male cell travels inside a pollen grain and the female cell waits inside an ovule. Students draw the cells 500 times life size, then sort twelve features by the cell they belong to.

We are learning to

• describe the form of the male and female gametes,
• link each feature of a gamete to the job it does,
• use a scale to compare sizes too small to see.

Success criteria

• I can draw the egg and the sperm to scale and say how many times wider the egg is than the sperm head.
• I can explain how two features help each gamete do its job.

You need

• rulers; the cell cards (third sheet), one set per pair, with scissors,
• the worksheet (next sheet), one per student.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the cells, the board and the drawing in Session A, and the cards and Part C in Session B.

Watch for these ideas

• “The sperm brings the instructions and the egg just feeds it.” Each gamete carries half of the instructions.
• “The egg is bigger because it holds more instructions.” Its size is its food store.
• “Pollen is the plant’s sperm.” A pollen grain carries the male cell inside a tough coat; it does not swim.

Make it easier, make it bigger

• Easier: give the scaled lengths, and ask students only to draw and label.
• Bigger: a frog egg, laid in a pond, is about 1.5 mm across; a human egg is about 0.12 mm. Suggest why the frog egg needs a much bigger food store.

Answers and look-fors

• Part A: human egg 120 µm, drawn 60 mm; human sperm 55 µm, drawn 27.5 mm; human sperm head 5 µm, drawn 2.5 mm; a pollen grain 30 µm, drawn 15 mm. The egg is 24 times as wide as the sperm head is long.
• Part B: sperm A, D, F, G, L; egg B, E, I, K; both C, H, J.
• Part C: 1. The tail and the mitochondria: the sperm must swim to the egg, and swimming needs energy. 2. The food store makes it large, so it cannot move; it feeds the new individual for its first days. 3. Each gamete has half the instructions, so the zygote gets a full set, half from each parent. 4. Most sperm never reach an egg, so making millions raises the chance that one does.
• Bigger: a frog embryo must live on the food in its egg until the tadpole can feed itself; a human embryo is soon fed through the mother’s body.

Small and mobile, large and stocked

A. Cells 500 times life size

1 mm = 1000 µm (micrometres). To draw a cell 500 times life size, multiply its real size by 500, then turn µm into mm.

Draw the egg and the whole sperm to this scale, side by side, and label the tail, the head and the food store.

B. Our sort

C. Questions

Sperm, egg, or both?

Cut out the cards. Lay down the three grey heading cards, then sort the features under them.

Teacher note: the piles are not the same size. The answer letters are in the plan.

Inside a flower

A flower is the reproductive organ of a flowering plant, and its form suits its job. The male part, the stamen, is a stalk called the filament with an anther on top that makes pollen. The female part, the carpel, has a sticky stigma that catches pollen, a style that holds the stigma up, and an ovary at the base that holds the ovules. Petals attract the animals that carry pollen, and sepals protect the bud. Students take a large flower apart from the outside in, record each part, and label a half-flower: a flower drawn as if cut from top to bottom.

We are learning to

• identify the reproductive organs of a flower by careful observation,
• describe the job of each part of the stamen and the carpel,
• record observations accurately in a table and a labelled diagram.

Success criteria

• I can find and name the parts of a real flower and label a half-flower.
• I can explain how the stigma, the anther and the ovary each suit their job.

You need

• one large flower for each pair, such as a lily or an alstroemeria; hand lenses, blunt scissors, white paper and sticky tape; a knife for the teacher only,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Safety and care: some sap and pollen irritate skin, so offer gloves; lily pollen stains clothes; wash hands afterwards. Keep lilies away from pets at home: they are poisonous to cats. Nothing is eaten.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the dissection in Session A, and Parts B and C in Session B.

Watch for these ideas

• “The petals are the reproductive parts.” Petals attract pollinators; the stamens and the carpel are the reproductive organs.
• “Pollen is the seed.” Pollen carries the male cell; a seed forms from an ovule after fertilisation.
• “Every flower has the same number of parts.” The numbers differ between species, which is one way botanists tell them apart.

Make it easier, make it bigger

• Easier: give pairs a flower already taken apart on a labelled card, and ask them to match each part to its job.
• Bigger: in a lily the sepals and petals look alike and are called tepals. Suggest how you could still tell which ring is which.

Answers and look-fors

• Part A, an example lily: 6 tepals in two rings of three, 6 stamens, a stigma with 3 lobes, and about 42 ovules in the ovary.
• Part B: 1 stigma, 2 style, 3 ovary, 4 ovule, 5 anther, 6 filament, 7 petal, 8 sepal.
• Part C: 1. The stigma is sticky, so pollen grains that land on it stay there. 2. The anther splits open to release dusty pollen that brushes onto visitors or blows away. 3. The ovary holds the ovules; after fertilisation the ovules become seeds and the ovary becomes the fruit. 4. To make sure pollen lands on the stigma from another flower, many flowers hold their anthers and stigma apart.
• Bigger: the outer ring is attached lower down and covers the bud; the inner ring is attached higher and often looks slightly different.
• Exit tickets: 1. The stamen: a filament and an anther. 2. The carpel: stigma, style and ovary. 3. The ovule, inside the ovary.

Inside a flower

A. Our flower, from the outside in

B. Label a half-flower

Write the part at each number. Use the word bank.

C. Questions

Exit tickets

Cut out one ticket for each student.

Pollen on the move

Pollination is the move of pollen from an anther to a stigma of the same species. A flower cannot walk to another flower, so it relies on a carrier. Animal-pollinated flowers attract insects, birds or small mammals with colour, scent and nectar; in Australia honeyeaters, and even the tiny honey possum, carry pollen between banksia and grevillea flowers. Wind-pollinated flowers, such as grasses and she-oaks, spend their effort on huge amounts of light pollen and on feathery stigmas instead. Students compare two kinds of flower, look at their pollen, and sort twelve features.

We are learning to

• explain what pollination is, and how it differs from fertilisation,
• compare the form of animal-pollinated and wind-pollinated flowers,
• link each feature of a flower to the carrier of its pollen.

Success criteria

• I can sort the features by the kind of pollination and explain one from each pile.
• I can say how pollination and fertilisation differ.

You need

• for each pair: a flower with bright petals (such as a grevillea or a daisy) and a grass head or a she-oak sprig; sticky tape, a hand lens or a microscope,
• the pollination cards (third sheet), one set per pair, with scissors, and the worksheet (next sheet).

Care: grass pollen can set off hay fever, so students who react can look at pollen already sealed under tape. Wash hands afterwards.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the two flowers in Session A, and the cards and Part C in Session B.

Watch for these ideas

• “Pollination is the same as fertilisation.” Pollination moves the pollen; fertilisation comes later, when the male cell joins the female cell in the ovule.
• “Only bees pollinate.” Many insects, birds, bats and small mammals do; in Australia honeyeaters pollinate many native plants.
• “Grasses have no flowers.” Grasses flower; their flowers are small and plain because they need no animal visitors.

Make it easier, make it bigger

• Easier: sort the cards about petals and pollen first, then the rest.
• Bigger: wind-pollinated plants make far more pollen than animal-pollinated ones. Explain why, and what this means for people with hay fever.

Answers and look-fors

• Part A, for example: the bright flower has large coloured petals, a scent, nectar and sticky pollen on anthers inside the flower; the grass has no petals, dangling anthers, feathery stigmas and fine, smooth pollen.
• Part B: animal-pollinated B, C, E, H, K; wind-pollinated A, F, J, L; both D, G, I.
• Part C: 1. Pollination moves pollen from an anther to a stigma; fertilisation is the joining of the male and female cells inside the ovule, which happens afterwards. 2. Colour, scent and nectar draw animals in, and sticky pollen clings to them. 3. Feathery stigmas net pollen from the air, and huge numbers of light grains make it likely that a few reach a stigma.
• Bigger: the wind carries pollen in every direction, so almost all of it lands somewhere useless; making huge amounts is the only way to be sure some reaches a stigma. That same pollen, breathed in, sets off hay fever.

Pollen on the move

A. Two flowers

B. Our sort

C. Questions

Animal-pollinated, wind-pollinated, or both?

Cut out the cards. Lay down the three grey heading cards, then sort the features under them.

Teacher note: the piles are not the same size. The answer letters are in the plan.

Inside or outside?

Fertilisation joins a male and a female gamete into one new cell, the zygote. Sperm must swim, so many animals that live in water fertilise outside the body: most frogs and fish, and corals, release eggs and sperm into the water, often in huge numbers. Animals on land fertilise inside the female’s body, where the gametes stay wet and protected; reptiles, birds and the platypus then lay eggs with a shell, and most mammals keep the young inside. Flowering plants solve the same problem with pollen: a pollen grain on a stigma grows a tube down the style that carries the male cell to the ovule. Students compare five animals found in Australia: how many young each has from one breeding, where fertilisation happens, and the care the young get.

We are learning to

• compare internal and external fertilisation,
• analyse data on numbers of young and the care they get,
• explain the trade-off between many young with no care and few young with a lot of care.

Success criteria

• I can say where fertilisation happens for each animal, and why water matters.
• I can use the data to explain why some animals have thousands of young and others one.

You need

• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and Part A in Session A, and Parts B and C in Session B.

Watch for these ideas

• “Animals that lay eggs fertilise outside the body.” Birds, reptiles and the platypus fertilise inside, then lay eggs with a shell.
• “More young means more success.” Most of a cane toad’s eggs and tadpoles die; each joey gets months of care and a much better chance.
• “Pollination is fertilisation.” Fertilisation happens in the ovule, after the pollen tube has reached it.

Make it easier, make it bigger

• Easier: work the first ratio together on the board, and ask students for the rest.
• Bigger: corals on the Great Barrier Reef release their eggs and sperm on the same few nights each year. Give two reasons this helps external fertilisation.

Answers and look-fors

• Part A: cane toad 20,000 times, green sea turtle 100 times, emu 10 times, platypus 2 times; the red kangaroo itself, 1.
• Part B: 1. The cane toad: it fertilises outside the body, in water. 2. The more care the young get, the fewer young there are. 3. The cane toad has 200 times as many young as the green sea turtle, and neither cares for them; most die, so a large number is needed for a few to survive. 4. Sperm must swim, and gametes dry out in air; inside the body they stay wet and protected.
• Part C: the pollen grain on the stigma grows a tube down through the style into the ovary, and the male cell travels down it to an ovule, so no water is needed.
• Bigger: eggs and sperm released together are far more likely to meet, and so many are released at once that predators cannot eat them all.
• Exit tickets: 1. Inside the female’s body. 2. Outside the body, in water. 3. With care, each young has a better chance of surviving, so fewer are needed.

Inside or outside?

A. Five animals found in Australia

Numbers are rounded, typical values for one breeding. In the last column, work out how many times as many young as the red kangaroo.

B. Questions

C. Plants too

Draw a stigma, a style and an ovary with one ovule. Add a pollen grain on the stigma, and draw the tube it grows to carry the male cell to the ovule.

Exit tickets

Cut out one ticket for each student.

From flower to seed

After fertilisation, the work of the flower moves inside the ovary. Each fertilised ovule grows into a seed: an embryo plant with a store of food and a tough coat. The ovary around the ovules swells into the fruit, while the petals and stamens wither and fall. A pea pod tells the whole story: the pod is the ripened ovary, each pea is a fertilised ovule, the dry thread at the tip is what is left of the style and stigma, and the small flat ovules between the peas are ones that did not grow, usually because they were not fertilised. Students open pea pods and count both, take apart a soaked broad bean, and think about how seeds travel.

We are learning to

• trace how an ovule becomes a seed and an ovary becomes a fruit,
• identify the parts of a seed and the job of each,
• use counts to work out what share of the ovules were fertilised and grew.

Success criteria

• I can point to the remains of the flower on a pea pod and say what each part became.
• I can calculate the percentage of ovules that grew into peas, and explain the rest.

You need

• fresh pea pods, one or two for each pair; broad beans soaked in water overnight; hand lenses and paper towel,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Care: nothing is eaten, even the peas. Students with a pea or bean allergy can observe without handling. Wash hands afterwards.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the pods in Session A, and the bean and Part C in Session B.

Watch for these ideas

• “Fruits are sweet.” In science a fruit is a ripened ovary holding seeds: a pea pod, a capsicum and a tomato are all fruits.
• “A seed is just a baby plant.” It is an embryo together with a food store and a protective coat.
• “Every ovule becomes a seed.” Only ovules that are fertilised grow into seeds.

Make it easier, make it bigger

• Easier: use the example class counts in Part A for the calculations.
• Bigger: name three ways seeds travel away from the parent plant, with an example of each, and explain why moving away helps.

Answers and look-fors

• Part A, example class: 6.4 peas per pod on average; 64 peas and 9 small flat ovules, so 73 ovules in all; 88% of the ovules grew into peas.
• Part B: the seed coat protects the seed; the two large halves store food; the embryo, a tiny root and shoot, sits between them at one edge.
• Part C: 1. The pod, the ovary, became the fruit; the peas, the ovules, became seeds. 2. The sepals at the stalk end, and the remains of the style and stigma at the tip. 3. They were not fertilised, so they did not grow. 4. The food store feeds the embryo as it starts to grow, until its first leaves can make food.
• Bigger: for example, the wind (a dandelion seed’s parachute), animals (fruit eaten by birds, or burrs caught in fur), water (a coconut), ants (wattle seeds). Seeds that land away from the parent do not compete with it for light, water and space.
• Exit tickets: 1. A fertilised ovule. 2. The ovary. 3. It feeds the embryo until the young plant can make its own food.

From flower to seed

A. Peas and ovules

An example class opened ten pods. Add your own pod in the last column.

B. Inside a broad bean

Draw the two halves of your bean, opened like a book. Label the seed coat, the food store and the embryo (its tiny root and shoot).

C. Questions

Exit tickets

Cut out one ticket for each student.

One parent: plants

Asexual reproduction needs only one parent and no gametes: a part of the parent grows into a new individual that is an exact genetic copy, a clone. Many plants do it on their own. Strawberries send out runners, garlic bulbs split into cloves, potatoes grow tubers, and spider plants grow plantlets on long stems. Gardeners copy plants the same way with cuttings, because every cutting grows into a plant just like its parent. Students set up mint cuttings in water to check in Lesson 9, match six plants to the part that grows a new plant, and graph an example of root growth.

We are learning to

• describe asexual reproduction in plants, and why the offspring are clones,
• identify the part of a plant that grows a new plant,
• graph growth over time and describe the pattern.

Success criteria

• I can set up a cutting and explain why it will grow into a clone.
• I can graph the root growth and say when the roots first appeared.

You need

• mint stems (or another soft-stemmed plant), scissors, small jars of water and masking tape for labels; a spider plant with plantlets to show,
• the worksheet (next sheet), one per student, and the cuttings record sheet (third sheet), one per pair.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the cuttings in Session A, and Parts A to C in Session B.

Watch for these ideas

• “Only simple living things reproduce asexually.” Many flowering plants do, and so do some animals, such as hydra.
• “Clones always look exactly alike.” They carry the same instructions, but a clone grown in shade can look different from one grown in sun.
• “Cuttings are a gardening trick, not reproduction.” A cutting grows into a new, separate plant from one parent: that is asexual reproduction.

Make it easier, make it bigger

• Easier: each pair sets up one cutting, and the class reads the example data together for Part B.
• Bigger: a fruit tree grown from a cutting often fruits years sooner than one grown from seed. Suggest why.

Answers and look-fors

• Part A: Strawberry E, Garlic C, Potato F, Spider plant A, Mint D, African violet B.
• Part B: no roots until day 4; after that the mean root length grows faster and faster, reaching 25 mm by day 14.
• Part C: 1. The cutting grows from part of one parent, with no gametes joining, so it has exactly the same instructions. 2. Roots grow from the nodes, so a node must be in the water. 3. For example: it is quick, it needs no flowers or pollinators, and every new plant has the prize plant’s features.
• Bigger: the cutting comes from a plant that is already old enough to flower, so it does not have to grow through the young stage again.

One parent: plants

A. Which part grows the new plant?

Write the letter of the part next to each plant.

B. An example: six mint cuttings

C. Questions

Our cuttings

Check the jars on these days. Count the roots on each cutting and measure the longest one. Top up the water each time.

Bring this sheet to Lesson 9. A cutting that rots or grows no roots is a result too: write down what happened.

Copies in a hurry

Single-celled living things can copy themselves very fast. A yeast cell, a single-celled fungus, can grow a small bud that swells and breaks away as a new cell: budding. A bacterium has no nucleus; it copies its single loop of DNA, grows, and splits down the middle into two equal cells: binary fission. In ideal conditions some bacteria divide every 20 minutes, so their numbers double again and again. Students look at living yeast under a microscope and count the budding cells, then model binary fission with numbers. No bacteria are grown in class.

We are learning to

• describe budding and binary fission as one parent making copies,
• use a microscope to observe and count cells,
• model growth by doubling, and explain why it becomes so fast.

Success criteria

• I can find a budding yeast cell and draw it, and work out the percentage of cells budding.
• I can complete the doubling table and explain what it shows.

You need

• a teaspoon of dried yeast and a teaspoon of sugar in 100 mL of warm (not hot) water, mixed 20 minutes before the lesson; droppers, microscopes, slides and coverslips,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Safety: hold slides and coverslips by their edges, and report any breakage. Wash hands afterwards. Nothing is grown on plates: bacteria are only modelled.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the yeast in Session A, and Parts B and C in Session B.

Watch for these ideas

• “Bacteria have a nucleus like our cells.” A bacterium has no nucleus; its DNA is a loop lying in the cell.
• “Doubling is just adding the same amount each time.” Each doubling adds as many cells as there already are, so the growth speeds up.
• “Bacteria really can double forever.” Food runs out and waste builds up, so real growth slows and stops.

Make it easier, make it bigger

• Easier: count in three fields of view, and use the example counts for the percentage.
• Bigger: one bacterium dividing every 20 minutes for 7 hours would make how many cells? Why does this never happen in a real kitchen?

Answers and look-fors

• Part A, example: 100 cells, 30 of them budding, so 30% of the cells were budding.
• Part B: 0 min 1, 20 min 2, 40 min 4, 60 min 8, 80 min 16, 100 min 32, 120 min 64, 140 min 128, 160 min 256, 180 min 512.
• Part C: 1. One parent, no gametes, and the new cells are copies of the parent. 2. After 180 minutes there are 512 cells. 3. Every doubling adds as many cells as there already are, so each step adds more than the one before. 4. Food runs out, waste builds up and the space fills, so the growth slows and stops.
• Bigger: 7 hours is 21 doublings, so 2,097,152 cells. Real conditions are rarely ideal, and food, space and the cold of a fridge hold bacteria back.
• Exit tickets: 1. Budding. 2. Binary fission. 3. Clones: exact copies of the parent.

Copies in a hurry

A. Yeast at 400 times

Draw one budding yeast cell as you see it.

B. Binary fission: a model

One bacterium, in ideal conditions, divides every 20 minutes. Fill in the number of cells.

C. Questions

Exit tickets

Cut out one ticket for each student.

Sexual or asexual?

Some living things reproduce in only one way, and many can do both. Sexual reproduction needs two parents, gametes, and usually more time and energy: flowers, pollinators or a mate, and fertilisation. Its reward is variation, because each offspring carries a different mix of its parents’ instructions. Asexual reproduction needs one parent and no mate, so it is fast and sure, but every offspring is a clone. Students sort twelve examples by the route each shows, then weigh the two routes against each other.

We are learning to

• classify examples as sexual or asexual reproduction, or both,
• compare the benefits and the costs of each route,
• explain why some living things use both.

Success criteria

• I can sort the twelve examples and justify the cards in the “both” pile.
• I can give a benefit and a cost of each route.

You need

• the route cards (third sheet), one set per pair, with scissors,
• the worksheet (next sheet), one per student.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the cards in Session A, and Parts B and C in Session B.

Watch for these ideas

• “Asexual reproduction is a lesser kind.” It is fast and sure, and many very successful species rely on it.
• “Plants reproduce asexually and animals sexually.” Most plants also make seeds, and some animals, such as hydra, bud.
• “Variation means something has gone wrong.” Variation is the ordinary difference between individuals, from mixing two parents.

Make it easier, make it bigger

• Easier: sort the cards that name one parent or two parents first.
• Bigger: a plant spreads by runners through a good season, and makes seeds before a dry summer. Explain why this pattern helps it survive.

Answers and look-fors

• Part A: sexual reproduction A, C, G, I, J; asexual reproduction B, E, H, L; both in one organism D, F, K.
• Part B: how many parents: two; one. do gametes join: yes, at fertilisation; no. how fast: slower: flowers, mates and growth take time; fast. needs a mate or a pollinator: yes; no. the offspring: vary from each other and from the parents; clones of the parent. a risk: no mate or pollinator, no young; one disease can harm every copy.
• Part C: 1. Each card in the “both” pile names two processes in one living thing: copies of one parent, and seeds or eggs from gametes joining. 2. Variation: when conditions change, some offspring are likely to survive. 3. Speed and no need for a mate: one well-suited plant can fill a good patch of ground quickly.
• Bigger: runners fill good ground fast while it lasts; seeds are varied, can travel, and can wait out the dry summer in the soil.

Sexual or asexual?

A. Our sort

B. Weigh them up

C. Questions

Sexual, asexual, or both?

Cut out the cards. Lay down the three grey heading cards, then sort the examples under them.

Teacher note: the piles are not the same size. The answer letters are in the plan.

Clones and a changing world

Variation is the difference between individuals of the same species, and sexual reproduction makes it by mixing two parents. It matters most when the world changes. Most of the bananas sold in Australia are one variety, Cavendish, grown from suckers and small plants taken from a parent, so the plants in a plantation are clones. A soil fungus that causes Panama disease wiped out the banana most people ate until the 1950s, and a newer form, tropical race 4, reached a farm in north Queensland in 2015 and kills Cavendish plants. Students model a disease sweeping two fields of 24 plants, one of clones and one varied, then measure the roots on their Lesson 6 cuttings.

We are learning to

• explain how variation helps a species survive when conditions change,
• use a model to compare a population of clones with a varied population,
• evaluate how well a model matches the real situation.

Success criteria

• I can count the survivors in both fields after each disease and explain the pattern.
• I can name one way the model is unlike a real banana farm.

You need

• the worksheet (next sheet), one per student, and the exit tickets (third sheet),
• the Lesson 6 cuttings, their record sheets and rulers.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and the fields in Session A, and the cuttings in Session B.

Watch for these ideas

• “Plants change to survive a disease.” A plant cannot change its instructions; the plants that already differ in a useful way survive and reproduce.
• “Clones are always weak.” Clones of a well-suited parent can do very well, until the conditions change.
• “Variation guarantees survival.” It makes it likely that some individuals survive, not certain.

Make it easier, make it bigger

• Easier: count the survivors of Disease 1 only, then discuss Disease 2 together.
• Bigger: scientists are breeding and testing bananas that resist tropical race 4. Explain why they search among many different banana plants, and how the need for a safe supply of bananas steers this research.

Answers and look-fors

• Part A: disease 1 (kills below 3): clones 0 of 24, varied 11 of 24; disease 2 (kills below 2): clones 24 of 24, varied 17 of 24.
• Part B: 1. The clone field is all or nothing: every plant has the same resistance, so a disease kills all of them or none. 2. The varied field kept some plants after both diseases, and those survivors can reproduce. 3. For example: real resistance is not one number, a disease spreads over time and through soil, plants differ in more than one feature, and the numbers here are made up.
• Part C: the cuttings are clones, so differences between them come from their surroundings or the piece of stem, such as light, water or a node out of the water; a fair comparison keeps those the same.
• Bigger: only a plant that already differs, with some resistance, can be bred from; the more varied the plants they test, the better the chance of finding one. Bananas feed many people and support farms, so the need for a safe supply directs money and effort to this research.
• Exit tickets: 1. Every plant would be harmed, because they are copies with the same weakness. 2. Variation. 3. It is fast and needs no mate.

Clones and a changing world

A. Two model banana fields

Each number is one plant’s resistance to disease, from 0 (none) to 4 (strong). A disease kills every plant whose resistance is below its strength.

B. Questions

C. Our cuttings

Exit tickets

Cut out one ticket for each student.

Show what we know

The term comes together. In the task, students read short facts about three living things that reproduce in more than one way, a coral on the Great Barrier Reef, a wattle tree and a potato crop, and explain how each reproduces and how that helps it survive. Then they sit the eight-question final check, and the class plays the unit quiz as a game on the board.

We are learning to

• apply what we know about gametes, organs and fertilisation to new living things,
• tell sexual and asexual reproduction apart in a written description,
• explain how each route helps a species survive.

Success criteria

• I can complete the task for all three living things, using evidence from the facts.
• I can answer the final check on my own.

You need

• the task (next sheet) and the final check (third sheet), one each per student,
• the interactive unit open on the board for the quiz; mini whiteboards if you have them.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the routes and the task in Session A, and the final check and the quiz in Session B.

Watch for these ideas

• Students who call a coral’s budding sexual because the coral is an animal: ask how many parents, and whether gametes join.
• Students who mix up pollination and fertilisation in the wattle row.
• Students who say potato clones are a mistake: a reliable crop is the reason farmers plant tubers.

Make it easier, make it bigger

• Easier: underline the sexual reproduction in each set of facts in one colour and the asexual in another before writing.
• Bigger: choose a fourth living thing that reproduces in two ways, and complete a row for it.

Answers and look-fors

• Task table: coral on the Great Barrier Reef: sexual, eggs and sperm are released into the sea and fertilised outside the body; asexual, polyps bud off new polyps, and a broken piece can grow into a new colony; survival, spawning makes varied young that drift to new reefs; budding grows a colony fast where conditions suit it. a wattle tree: sexual, insects and birds carry pollen between flowers; fertilised ovules become seeds in pods; asexual, not in these facts; survival, varied seeds can wait in the soil for years and grow after a fire, even if the parent tree dies. a potato crop: sexual, flowers make seeds, which breeders grow to find new, varied plants; asexual, farmers plant pieces of tuber, so the plants in a field are clones; survival, clones of a good variety give a reliable crop; seeds give the variation needed to breed new varieties.
• Task questions: 1. Outside the body, in the sea. 2. Insects and birds. 3. Every plant grows from a piece of tuber of the same parent line, so they are clones. 4. Every plant would be harmed, because they share the same weakness; breeders can grow varied plants from seed and look for ones that resist the disease.
• Final check: 1. Egg. 2. The anther. 3. The ovary. 4. Pollination moves pollen from an anther to a stigma; fertilisation is the joining of the male and female cells in the ovule, afterwards. 5. Binary fission. 6. They come from one parent with no gametes joining, so they have exactly the parent’s instructions. 7. A frog. 8. The offspring vary, so some are likely to have features that let them survive the disease and reproduce.
• Mark the task against the rubric in the assessment kit; the check covers gametes, organs, fertilisation and the two routes.

Three living things, two routes

Show what we know