Biology comes from two Greek words
Bios = Life Logos = Study or knowledge
Biology – is the scientific study of living things. Today the scope of biology encompass living things and their interaction with non-living things in their physical environment.
Main branches of biology
In living things, often we think of animals and plants. These two make main branches of biology, namely:
i/. Zoology scientific study of animals
ii/. Botany scientific study of plants.
However, in the world of living organisms there are other organisms which are neither plants nor animals; example: bacteria, fungi, protoctista and viruses. Since biology is more than animals and plants, we have other branches of biology.
Other branches of biology
- Bacteriology is the scientific study of bacteria.
- Mycology is the scientific study of fungi.
- Microbiology is the scientific study of micro-organisms.
- Cytology is the scientific study of the structure and function of cells.
- Dermatology is the medical study of the skin and its diseases.
- Genetics is the study of inheritance and variations in inheritance.
- Hydrobiology is the study of aquatic life forms
- Ichthyology is the study of fish.
- Etiology (Aetiology) is the study of causes of diseases.
- Ethology is the study of animal behaviour.
- Entomology is the study of insects.
- Virology is the scientific study of virus.
- Taxonomy is the scientific study of classification.
- Anatomy is the scientific study of structure of organisms.
- Protozoology is the scientific study of protozoa.
- Physiology is the study of how the bodies of organisms and their various parts functions.
- Pharmacology is the study of properties of drugs and their effects on living organisms.
- Life, is the state of being alive or existing. That is the ability to grow and reproduce. All living things are composed of one or more cells.
- Cell, is the basic unit of life. A cell is composed of nucleus, cytoplasm and cell membrane.
- Organism – (Living things). Is an individual living system, such as animal, plant or micro-organisms bacteria) that is capable of reproduction, growth and maintenance of worn out tissues.
- Non-living thing- is anything that does not exist or is dead.
1. Nutrition or feeding
2. Movement and locomotion.
3. Growth and development.
5. Sensitivity and Irritability or Response.
7. Gaseous exchange.
- Nutrition (Feeding).
All living things take in and assimilate materials (food) for growth, maintenance and repair of worn out tissues.
Mode of Feeding,
Autotrophic Nutrition. Where green plants (and some micro-organisms) make their own food from inorganic substances by the process of photosynthesis.
Heterotrophic Nutrition, where by organisms (animals) feed on readymade organic matter (other organisms)
- i) Herbivores, are animals that feed on plants e.g. cows, giraffes
- ii) Omnivores, are animals that feed on other animals as well as plants, e.g. human being
iii) Carnivores, are animals that eat other animals, i.e. Leopard and lion.
Saprophitic nutrition: feed on dead decay matter (i.e.: remains or products of other animals.)
- Movement and locomotion:
Movement is the act of changing position or posture. It can involve the whole body or part e.g. plants move by growing: roots towards source of water; stem towards light.
Locomotion: is the movement of the whole body: change in position.
Why do organisms move?
- In search of food
- Search of a mate.
- Away from negative stimuli e.g. predators, chemicals, fire, secure protection.
- Towards positive stimuli e.g. light, gravity, chemicals & water.
- Growth and development:
Growth: Irreversible increase in size and mass.
Development: irreversible change in the complexity and structure of living things: (e.g. ability to reproduce when you reach puberty or ability to speak.)
The ability to give rise to the new individual of the same kind (species).
- i) Sexual reproduction: involves mating of male and female organisms e.g. human, maize.
- ii) Asexual reproduction: one parent only e.g. by splitting (amoeba) or vegetative propagation (sugar cane, banana.).
- Sensitivity and Irritability (response).
Sensitivity: ability to detect changes in the surroundings using sense organs in animals ( eyes, skim, ears, nose, tongue) and hormones in plants.
Irritability (response): ability to react to changes in the immediate environment e.g. temperature, humidity, light, pressure and chemicals.
- Respiration: is the process by which food substances are chemically broken down in all living cells to release energy, carbon dioxide and water. The energy is used for:
- i) Muscular contraction.
- ii) Conduction of nerve impulse (sensitivity)
iii) Growth and development.
- iv) Repair of worn out tissues.
- v) Secretion of enzymes.
- vi) Function of body organs (kidney, heart, liver, brain etc.)
- Gaseous exchange: process whereby respiratory gases (oxygen and carbon dioxide) are passed across the respiratory surfaces.
- Excretion: process by which excess waste and harmful materials resulting from body metabolisms are eliminated from the body.
- Heredity: all living things have a genetic system that is based on the replication of nucleic acid (DNA). A genetic system is the only characteristics which defines life properly.
- Death: is the end of life also it is the point at which processes and organs that maintain an organism no longer function, e.g. permanent cessation of heart beat in human.
- i) Necrosis: death of a cell due to external damages or action of toxic substances.
- ii) Apoptasis: death of a cell, which occur naturally as a part of normal development within an organism.
NOTE: Some of these characteristics may be seen in some of non-living things, e.g. movement of wind or stone, disposition of seeds; but the actions in the living organisms are from within.