Plant & animal reproduction
Describe the life process of reproduction in some plants and animals, including sexual and asexual reproduction in plants
What a learner can do afterwards
- Describe sexual reproduction in flowering plants through pollination, fertilisation and seed development
- Explain how strawberry runners, additional bulbs and rooted cuttings can produce new plants asexually
- Compare development in laid eggs with live birth in mammals such as cats, without assuming that birth method determines parental care
1 · Read
Pollination moves pollen to a flower's stigma. A pollen grain can grow a tube towards an ovule, which contains an egg cell. A male cell from the pollen travels through the tube and joins the egg cell. This joining is fertilisation. The ovule can then develop into a seed. Joining male and egg cells is sexual reproduction. These cells can come from the same plant or from different plants.
Asexual reproduction makes a new plant from one parent without male and egg cells joining. A strawberry runner is a spreading stem. Roots and shoots can grow at its joints and form new plants. Tulips and onions can form additional bulbs that grow into separate plants. An old bulb sprouting again is the same plant regrowing; additional bulbs can produce more plants.
With an adult's help, Mia takes a coleus stem cutting that includes a leaf joint. She puts it in moist soil. If roots and shoots develop, the cutting can become a separate plant. This is asexual reproduction: no male and egg cells join. The new plant usually shares the parent's inherited traits. Its size and health also depend on growing conditions.
Birds lay eggs, and many frogs lay eggs in water. Young develop inside these laid eggs and then hatch. Most mammals, including cats, dogs and elephants, give birth to live young that developed inside the mother. Platypuses and echidnas are mammals that lay eggs.
Egg-laying does not tell you how much care parents give. Hens warm eggs and care for chicks. Compare each animal's details: laid eggs or live birth, the number reported and the care observed. A count of eggs is not a count of young that survive. Two examples cannot prove a rule for every animal in their groups.
Fertilisation joins male and egg cells. Runners, additional bulbs and cuttings can produce plants asexually. Animals may hatch from laid eggs or be born live; parental care varies.
The plant and animal reproduction lesson, questions and flashcards were written for this dataset.
The readings were written for this dataset. Linked video: Sexual and asexual reproduction, attributed in the source catalog to Khan Academy. Video rights remain with its publisher.
More to read
Growing again or making another plant?
An old tulip bulb can send up leaves again. That is the existing plant growing. When additional bulbs develop into separate plants, the number of plants increases. That is reproduction.
A strawberry runner can form another plant at a joint along its stem. Roots grow into the soil and a new shoot grows above it. A coleus stem cutting can also develop roots and shoots under suitable conditions.
These methods do not require male and egg cells to join. They are asexual reproduction from one parent. New plants usually share the parent's inherited traits, but that does not make their appearance identical in every condition. Different amounts of light, water or nutrients can affect growth.
Pollen arriving is not fertilisation
A pollen grain on a stigma shows that pollination has happened. It does not show that a seed has formed.
A pollen tube can grow towards an ovule inside the flower. A male cell from the pollen travels through the tube. Fertilisation happens when this cell joins an egg cell in the ovule. The ovule can then develop into a seed containing a young plant.
This joining of reproductive cells is sexual reproduction. The cells may come from different plants, but two separate parent plants are not always needed. Pollen and egg cells can come from the same plant.
Keep the events separate when explaining seed formation: pollen arrives, a tube grows, reproductive cells join, and a seed can develop.
Compare birth and care separately
A chick develops in an egg laid outside its mother's body. A kitten develops inside its mother and is born live. Most mammals give birth to live young. Platypuses and echidnas are egg-laying mammals.
Birth method does not settle how much care the young receive. Hens warm eggs and care for chicks. An egg-laying parent does not always leave its young alone.
For each animal, record what the example actually tells you. Does it describe laid eggs or live young? How many are reported? What care is observed?
An egg count cannot tell you how many young survive. A comparison of two examples also cannot establish a rule for every animal in their groups.
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