ACARA v9 CONTENT DESCRIPTION “describe the form and function of reproductive cells and organs in animals and plants, and analyse how the processes of sexual and asexual reproduction enable survival of the species”
Builds on cells as the basic units of living things. Here we look at the cells and organs that make new living things, and at the two ways a species passes life on to the next generation.
Reproductive cells: the gametes
A reproductive cell is called a gamete. Gametes come in two forms: a small mobile male cell and a larger food-filled female cell. In animals these are the sperm and the egg, or ovum. In flowering plants the male cell is carried inside a pollen grain, and the female cell sits inside an ovule. Each gamete carries only half of the instructions for a new individual, which is why two of them are needed.
Reproductive cells: the gametes
A sex cell is called a gamete. Every gamete comes in a small mobile male form and a larger food-filled female form. Toggle between animals and plants to compare the two pairs.
SpermEgg (ovum)
Sperm: small and able to swim to the egg. Egg (ovum): large and stocked with food for the new cell. The same pattern of a small male cell and a large female cell appears in both animals and plants.
Reproductive organs
Gametes are made by reproductive organs. In animals these are named plainly: the testes produce sperm and the ovaries produce eggs. In a flowering plant the flower is the reproductive organ. It has a male part, the stamen, whose anther makes pollen, and a female part, the carpel, whose ovary holds the ovules and whose stigma catches pollen. The shape of each organ suits the gamete it makes or receives.
Reproductive parts of a flower
A flower is the reproductive organ of a flowering plant. It has a male part, the stamen, and a female part, the carpel. Click a part to highlight it and read its job.
Anther: The top of the stamen. It makes and holds the pollen.
Fertilisation makes a zygote
Sexual reproduction works by bringing two gametes together. When a male gamete joins a female gamete, the event is called fertilisation, and the single cell it forms is called a zygote. The zygote now holds a full set of instructions, half from each parent, and grows into a new individual. Because the new cell mixes two parents, the offspring is a little different from either one.
Fertilisation: two gametes become one
Sexual reproduction needs two gametes to join. This joining is called fertilisation, and the single cell it makes is called a zygote. Step through it.
Step 1. Two gametes start apart: a small male cell and a large female cell, each with half the instructions.
Two routes: sexual and asexual
There are two ways to make new living things. Sexual reproduction joins gametes from two parents, so the offspring carry a mix and show variation. Asexual reproduction uses just one parent, with no gametes joining; each offspring is an exact genetic copy, called a clone. Sexual reproduction gives variety among the offspring, while asexual reproduction is quick and needs only one parent.
Sexual and asexual reproduction
There are two routes to new individuals. Sexual reproduction joins two parents, so the offspring carry a mix. Asexual reproduction needs only one parent, so the offspring are exact copies. Toggle to compare.
Sexual reproduction joins a gamete from each of two parents. The offspring carry a mix of both sets of instructions, so each one is a little different. This variation is simply the result of combining two parents.
Ways living things reproduce asexually
Asexual reproduction is common across the living world. A strawberry plant grows new plants along a runner, and a gardener can grow a cutting the same way. Yeast and hydra make a bud that breaks away as a new individual. A bacterium copies its instructions and splits in two by binary fission. In every case one parent makes a copy of itself.
Examples of asexual reproduction
Many living things copy themselves from a single parent. Choose an example to see how one parent makes a new individual without any gametes joining.
A strawberry plant sends out a runner, a side stem. Where it touches the soil a new plant grows, identical to the parent. Cuttings work the same way.
How reproduction keeps a species going
No single organism lives forever, so a species continues only if its members make a new generation. Reproduction is how that happens: each generation produces the next, and so the species carries on across time. Sexual reproduction passes life on with variation among the offspring, while asexual reproduction passes it on quickly and reliably from one parent. Both processes have the same outcome, which is the survival of the species across the generations.
Quick self-check
1. What is a gamete?
2. Which part of a flower is the female reproductive organ?
3. What is formed when two gametes join at fertilisation?
4. How do the offspring of asexual reproduction compare with the parent?