Characteristics of Living Organisms
- Movement: action by an organism or part of an organism causing a change of position or place
- Respiration: the chemical reactions that break down nutrient molecules in living cells to release energy
- Sensitivity: ability to detect or sense changes in the environment (stimuli) and to make responses
- Growth: permanent increase in size and dry mass by an increase in cell number or cell size or both
- Reproduction: processes that make more of the same kind of organism
- Excretion: removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements
- Nutrition: taking in of nutrients which are organic substances and mineral ions, containing raw materials or energy for growth and tissue repair, absorbing and assimilating them
Concept & Use of a Classification System
- Organisms can be classified into groups by the features that they share
- Classification systems aim to reflect evolutionary relationships (change of adaptive features of a population over time, as a result of natural selection)
- Species: organisms which can reproduce successfully
- Morphology: the overall form and shape of their bodies e.g. wings or legs
- Anatomy: the detailed body structure determined by dissection
Binomial system
A system of naming species in which the scientific name of an organism is made up of two parts showing the genus (starting with a capital letter) and species (starting with a lower-case letter), written in italics when printed (therefore underlined when written)
e.g. Homo sapiens
Kingdom, Phylum, Class, Order, Family, Genus, Species
Kingdoms
- Animal: Multi-cellular ingestive heterotrophs (eat living organisms)
- Plant: Multi-cellular photosynthetic autotrophic (make their own food) organism with a cellulose cell wall.
- Fungi: Single celled or multi cellular heterotrophic organism with cell wall not made of cellulose, spread by spreading of spores in moist/dark/warm environment, saprotrophs (feed off dead organisms) or parasites
- Prokaryotes: Single celled organism with no true nucleus
- Protoctista: Single celled organism with a nucleus
Classifying Plants
- Flowering plants:
- They are plants with roots, stems and leaves
- Reproduce sexually by means of flowers and seeds
- Seeds are produced inside the ovary in the flower
| Monocotyledons | Dicotyledons |
| One cotyledon | Two cotyledons |
| Parallel veins | Veins netlike |
| Fibrous root | Taproot present |
| Floral parts in 3s | Floral parts in 4s or 5s |
Viruses and Bacteria
| Virus | Bacteria | |
| Covered by: | Protein coat | Cell wall |
| Cell membrane: | No | Yes |
| Cytoplasm: | No | Yes |
| Genetic material: | DNA or RNA – only a few genes | DNA – enough for several 100 genes |
| Living or not? | Non-living unless in host | Living |
Dichotomous Keys
Dichotomous key: uses visible features to classify organisms. It is which gives you a choice of two features and you follow the one that applies: each choice leads to another choice until the organism is narrowed down to its genus and finally species.