Scientific ideas, concepts and processes
Cells and Classification
A cell is the unit from which biological organisms are built and carries out life processes: movement, respiration, sensitivity, growth, reproduction, excretion, nutrition.
Bacteria and protoctists are made of a single cell (unicellular). Animals, plants and fungi are made of many cells (multicellular).
Plants are autotrophs- they make their own food in their leaves by photosynthesis. Animals are heterotrophs and must consume food.
Each living organism is part of a species. The binomial naming system for species is a latin name e.g. panther tigris.
Plant organs include stem, fruit, flower, seed, roots, leaves. Each organ has a specific function which enables the plant to survive and reproduce.
Plants and photosynthesis
Plants make food (carbohydrates) in their leaves by photosynthesis using carbon dioxide and water, producing glucose and oxygen.
The rate of photosynthesis depends on the temperature, availability of water and carbon dioxide and light levels.
Chlorophyll is the green chemical in the chloroplasts of plant cells which enables the plant to photosynthesise.
The rate of photosynthesis depends on limiting factors including temperature, sunlight and availability of water and carbon dioxide.
Leaves are adapted for photosynthesis with an epidermis, palisade cells, a spongy mesophyle layer and stomata allowing gas exchange.
Fertilizers
Plants need minerals from the soil which are dissolved in the water they take up through their roots.
Artificial fertilizers replace the nutrients removed from the soil when a plant is grown. They usually contain nitrogen, phosphorous and/or potassium.
Organic fertilizers are made from manure or other organic waste and also contain a mix of soil nutrients.
Different species of plant are adapted to grow in different conditions (light levels, temperature, soil, etc.)
Reproduction in plants
Plants can reproduce asexually, using runners or tubers. Asexual reproduction gives daughter plants which are genetically identical to their parents. Population growth is faster, but plants are more vulnerable to diseases as there is less genetic diversity in the population.
Some plants can reproduce sexually, with the flower structured with male and female structures for reproduction.
Plants can be wind-pollinated or pollinated by animals, and produce different flower structures for each type of pollination.
Fertilization is the process where male and female gametes fuse in the ovary.
Seeds
The seed contains the embryonic plant, the radical and plumule, a store of food in the cotelydon. It is enclosed in a testa, which contains a small hole for gas exchange.
Seed dispersal is important for plant reproduction and plants have many different adaptations including dispersal by wind and animals.
Seed germination occurs at a particular temperature and the seed grows using reserves of food stored in the cotelydon.
Plant adaptations
Plants are adapted to survive and reproduce in their natural habitat. Plant adaptations include adaptations for finding and conserving water, capturing sunlight, keeping warm and collecting minerals.
Humans use different parts of plants for food. Artificial selection breeds plant varieties with characteristics useful to humans. All crops were originally wild plants.
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