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Introduction to biology: Class 9 Biology
What biology is, its main branches, how it links with other sciences, and the levels of biological organisation from cell to biosphere.
Key points
Biology is the study of living things. The word comes from the Greek words bios, meaning life, and logos, meaning study. Biologists study how living things are built, how they work, how they grow, how they are related and how they interact with their surroundings.
Some major branches of biology:
- Morphology studies the form and structure of organisms.
- Anatomy studies the internal structure of organisms.
- Physiology studies the functions of the parts of organisms.
- Cell biology (cytology) studies cells.
- Genetics studies heredity and variation.
- Taxonomy studies the naming and classification of organisms.
- Ecology studies the relationships between organisms and their environment.
- Embryology studies the development of an organism before birth or hatching.
- Microbiology studies microscopic organisms such as bacteria and viruses.
- Biotechnology uses living organisms or their parts to make useful products.
Biology is linked with other sciences. Biochemistry joins biology and chemistry and studies the chemical reactions in living things. Biophysics applies physics to biology, for example the study of how the eye forms images. Biostatistics uses mathematics to analyse biological data, and environmental biology links biology with the study of the environment.
Levels of biological organisation, from smallest to largest:
- Cell: the basic unit of life.
- Tissue: a group of similar cells doing one job.
- Organ: tissues working together, such as the heart.
- Organ system: organs working together, such as the digestive system.
- Organism: a complete living thing.
- Population: organisms of the same species living in one place.
- Community: populations of different species living together.
- Ecosystem: a community together with its non-living surroundings.
- Biosphere: all the parts of the earth where life exists.
Knowledge of biology is used in medicine, agriculture, food production, animal husbandry, forestry, fisheries and environmental protection. Many careers depend on it, including doctor, nurse, pharmacist, agricultural scientist, biotechnologist, laboratory technologist and wildlife officer.
Study tip: Learn the levels of organisation as a list in order. It is asked in almost every paper.
Definitions and flashcards
Say the meaning first, then open the card to check.
Biology
The study of living things.
Morphology
The study of the form and structure of organisms.
Anatomy
The study of the internal structure of organisms.
Physiology
The study of how the parts of an organism work.
Taxonomy
The science of naming and classifying organisms.
Ecology
The study of the relationships between organisms and their environment.
Genetics
The study of heredity and variation.
Population
A group of organisms of the same species living in one area.
Community
All the populations of different species living in one area.
Ecosystem
A community of living things together with its non-living environment.
Biosphere
The part of the earth where life exists.
Biotechnology
The use of living organisms or their parts to make useful products.
Short questions with model answers
These are the kind of questions asked for 2, 3 and 5 marks. Try each one before opening the answer.
Define biology. From which words does the name come? (2 marks)
Biology is the study of living things. It comes from the Greek words bios, meaning life, and logos, meaning study.
Differentiate between morphology and anatomy. (2 marks)
Morphology studies the outer form and structure of organisms, for example the shape of a leaf. Anatomy studies the internal structure, for example the arrangement of tissues inside the leaf.
What is physiology? (2 marks)
Physiology is the branch of biology that studies the functions of the parts of living things, such as how the heart pumps blood.
What is meant by a population and a community? (2 marks)
A population is a group of organisms of one species living in one place. A community is made up of all the populations of different species living in the same place.
List the levels of biological organisation from the smallest to the largest. (3 marks)
Cell, tissue, organ, organ system, organism, population, community, ecosystem and biosphere.
What is biotechnology? Give two uses. (3 marks)
Biotechnology is the use of living organisms, or parts of them, to make useful products or to solve problems. It is used to produce medicines such as insulin and to make foods such as yogurt.
Explain how biology is related to chemistry and physics. (5 marks)
Biochemistry joins biology and chemistry. It studies the chemical reactions in living cells, such as respiration and digestion. Biophysics joins biology and physics. It uses the laws of physics to explain living processes, for example how the eye focuses light, how blood flows and how nerves carry electric signals. These links show that the sciences depend on each other.
Common mistakes
- Confusing morphology (outside form) with anatomy (inside structure).
- Writing the levels of organisation in the wrong order, or leaving out community or ecosystem.
- Using ecosystem and community as if they mean the same thing. An ecosystem includes the non-living environment.