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By the end of this unit you should be able to:·
Describe plants as multi-celled, photosynthetic living things
Describe photosynthesis as the process of using sunlight, water and carbon dioxide to produce food (glucose)
Recall that photosynthesis takes place in the chloroplasts and uses the pigment chlorophyll
Relate the green colour of plants to chlorophyll and the use of light energy (e.g. that green light is not used)
Identify the cuticle, stomata and guard cells on a leaf diagram and relate these to leaf processes (water shedding, gas exchange)
Relate the structure of the of the leaf to the processes of photosynthesis and transpiration
Explain how and why water is transported within plants
Describe the parts of a flower and relate this to pollination range: stigma, stamen, anther, ovule, pollen
Explain why plants cross-pollinate and give examples of pollination strategies
Explain why plants use seed dispersal strategies and give examples of these
Be aware of basic plant classification and be able to apply a key to identify which plant category a particular plant might belong to range: bryophytes, ferns, gymnosperms, monocotyledons, dicotyledons
Be aware of the appearance, Maori names and traditional uses of some NZ endemic plants
What is a plant?
What is a plant?
Most of the time it is reasonably obvious what a 'plant' is. All the photos below show plants.
There are some things that we might think are plants, but aren't:
Fungus
Seaweed
Lichen
The organisms above are not plants. Fungi are a separate kingdom of their own; they have differences in cell structure (cell walls are made of chitin, not cellulose) and they don't photosynthesise. Seaweeds are very similar to plants and are related to them; they are a type of algae. Lichens are a colony of two different organisms living together in a relationship that benefits both (a fungus and a cyanobacterium). Lichens and seaweed both photosynthesise.
Photosynthesis
Photosynthesis
One of the main characteristics of plants is that they make their own food from sunlight, a process called photosynthesis.
Plants were not the first organisms to photosynthesise and are not the only kingdom of organisms to do so.
Organisms that make their own food are called autotrophs. Before photosynthesis, the primitive organisms of the early Earth used chemosynthesis; they made their food using chemical energy, from sources such as hydrogen, rather than the energy of sunlight.
Photosynthesis evolved (that is, was 'invented' by living things) several times over in different organisms, each time a bit differently. The type of photosynthesis found in plants first appeared in organisms called cyanobacteria and used green chlorophyll.
Cyanobacteria are still around and are found in various forms, One well known form is the reef-building form called stromatolites, famously occurring at Shark Bay in Western Australia.
Stromatolites, Shark Bay
Scientists aren't quite sure how photosynthesis got from cyanobacteria to plants, but most think it happened when a protist 'ate' a cyanobacterium. This cyanobacterium then lived inside the protist in a mutually beneficial relationship. This cyanobacterium eventually became the chloroplasts of plants.
Video about evolution of plants here.
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