Reproduction in Plants Flashcards
What is sexual reproduction?
Is when there are two parents and there are two gametes which fuse in fertilisation and the offspring shares the genes of both parents.
What is asexual reproduction?
Is when there is only one parent, no gametes and no fertilisation occurs. The offspring is genetically identical to the parent.
What are the advantages of sexual reproduction?
-Variation
-Adapt and evolve quicker
DIS: slower, longer to grow family, don’t pass on many of your genes
What are some aspects of sexual reproduction in plants
- Sex cells are formed by meiosis
- Pollen grains are produced in the anther of the stamen
- Pollen contains the plant’s male gametes called sperm
- Ova are produced in the ovules and are the female gamete
What are the different ways pollination can occur?
Wind, Insect
How is the position of the stamen different for wind pollinated and insect pollinated flowers?
- Wind: Exposed so that wind can easily blow pollen away
- Insect: Enclosed within flower so that insect must make contact
How is the position of the stigma different for wind pollinated and insect pollinated flowers?
- Wind: Exposed to catch pollen blowing in the wind (hanging outside flower)
- Insect: Enclosed within flower so that insect must make contact
How is the type of stigma different for wind pollinated and insect pollinated flowers?
- Wind: Feathery to catch pollen blowing in the wind
- Insect: Sticky so pollen grains attach from insects
How is the size of petals different for wind pollinated and insect pollinated flowers?
- Wind: Small
- Insect: Large to attract insects
How is the colour of petals different for wind pollinated and insect pollinated flowers?
- Wind: Not brightly coloured, usually green (not waste energy to make this as not needed?)
- Insect: Brightly coloured to attract insects
How is the nectaries different for wind pollinated and insect pollinated flowers?
- Wind: Absent
- Insect: Present (nectar is a ‘reward’ for insects)
How is the pollen grains different for wind pollinated and insect pollinated flowers?
- Wind: Smaller, smooth inflated grains to carry in the wind (large quantity)
- Insect: Larger, sticky grains to stick to insects’ bodies
Why do plants generally ensure that they cross pollinate?
Greater chance of genetic variation
What is fertilisation?
The fusion of female and male gametes to produce a zygote in sexual reproduction, that undergoes cells division and develops into an embryo
Describe plant fertilisation
- Pollen lands on stigma on carpel
- Pollen tube grows down the style and enters the ovary and then enters the ovule through the micropyle
- The pollen then enters the ovum where it is fertilised to become a zygote
- There are also polar nuclei which are also fertilised to form cotyledons which provide a food source to the zygote
What is the female part of the plant called?
The carpel
What is the function of the stigma?
The platform on which the pollen lands
What is the function of the style?
A stalk which holds and supports the stigma in the best position
What is the function of the ovary?
A hollow chamber which contains the female gametes inside ovules. The ovules develop to form the walls of the ovary
What is the function of the micropyle?
Entry point for the male nucleus at fertilisation
What is the male part of the plant called?
The stamen
What is the function of the anther?
Contains four pollen sacs filled with pollen grains. Each pollen grain contains a male gamete.
What is the function of the filament?
A long stalk that holds and supports the anther in the best position to release pollen onto a visiting insect.
What is cross pollination?
Cross pollination is when pollen from a flower is transferred to the stigma of another flower (Sexual reproduction). They rely on insects or wind to help them pollinate.
What is self pollination?
Self pollination occurs when pollen from a flower is transferred to it’s own stigma
What is pollination?
The transfer of pollen from an anther to a stigma, so that the male gametes can fertilise the female gametes in sexual reproduction
Describe seed and fruit formation
- The zygote, (having been fertilised), develops into an embryonic plant with a small root (radicale) and small shoot (plumule)
- The other contents of the ovule develop into cotyledons which will be a food store for the young pant when the seed germinates. Some plants have one cotyledon (monocots) and some have two (dicots).
- The ovule wall hardens and becomes the testa or seed coat
- The ovary wall swells and becomes the fruit coat, this can take many forms depending on the type of fruit
Why do seeds disperse?
Too avoid competition of water, mineral ions and oxygen.
What are the different types of seed dispersal?
- Wind
- Water
- Animal (internal and external)
- Ballistic (explosive)
Why are seeds able to lie dormant?
- Because they are not using energy to grow when the conditions are not right (slow metabolism, very little respiration (like extreme hibernation)).
- When seeds are dispersed from the parent plant they are usually very dry and only contain 10% water. This low water content restricts a seed’s metabolism.
What happens when a seed germinates?
- Dormancy is broken
- The seed’s food store is broken down by enzymes respired aerobically
What conditions are needed for germination?
- Warm temperatures, so that enzymes can act efficiently (suitable temperature as depends on what type of seed it is)
- Water, to soften the testa and for chemical reactions in the seed to take place in solution
- Oxygen, for respiration (which provides energy for growth)
(4. pH (of soil) )
Describe germination
- The seed takes in water and starts to grow using its store of energy
- The first root starts to grow down into the soil
- The shoot grows up
- Finally extra roots grow and the first green leaves appear.
Describe how germinating seeds get energy from food stores
- A developed seed contains an embryo and a store of food reserves, wrapped in a hard seed coat
- When a seed starts to germinate, it gets glucose for respiration from its own food store. This gives it the energy it needs to grow. The radicle breaks through the testa and grows downwards into the soil (positive geotropism). The plumule grows upwards towards the light (negative geotropism)
- Once the plant has grown enough to produce green leaves it can get its own food for energy from photosynthesis.
Describe how plants reproduce asexually using natural methods
E.G Strawberry
- The parent strawberry plant sends out runners, fast-growing stems that grow out sideways just above the ground
- The runners take root at various points (a short distance away) and new plants start to grow)
- The new plants are clones of the parent strawberry plant so there is no genetic variation between them
Describe how plants reproduce asexually using artificial methods
- Gardeners can take cuttings from a good parent plant and then plant them to produce genetically identical copies (clones) of the parent plant
- These plants can be produced quickly and cheaply
Suggest a way in which animal and plant asexual reproduction must be different
A zygote is produced without fertilisation
What is fertilisation?
Fertilisation involves the fusion of a male and female gamete to produce a zygote that undergoes cell devision and develops into an embryo
What is germination?
The process by which the embryo plant in the seed starts to grow to the point where it is photosynthesising independently
