Biology Class 9 Chapter 1: The Science of Biology

Biology is the study of living organisms. The word comes from two Greek words: bios meaning life and logos meaning thought, reasoning or study. It helps us explain how living things relate to one another and to their surroundings.

Two questions: (1) Why are the leaves turning yellow? (2) Does the plant need more or less water or sunlight? Asking questions is the first step of science because science is the process of collecting information about the world; observation leads to a question, and the question leads to finding the answer.

(a) and (c) are biological because fish and bacteria are living organisms. (b) is not biological because ice is non-living and its melting point belongs to physics/chemistry.

• "We made every living thing from water" (Sura Ambia 21:30) – origin of life in water; living things have a common origin.
• "He made man from clay like the potter" (Sura Rehman, Ayat 14) – creation of man from water and clay.
• (Also: Sura Al-Mominoon, Ayat 14 – stages of development: drop, clot, little lump, bones, flesh.)

Living things consist of 60 to 90 percent water, and the Quran says every living thing was made from water. Because man shares all characteristics of life with other animals, the idea can be said for all living things, so they have a common origin.

Muslim scientists made great contributions to biology. The knowledge of Jabir bin Hayyan, Abdul Malik Asmai and Bu Ali Sina contributed a lot to the development of present-day knowledge of plants and animals.

Stages: drop → clot → little lump → bones → bones clothed with flesh. The branch is embryology, which studies the development of an organism from a fertilized egg.

• Botany – the study of plants.
• Zoology – the study of animals.
• Microbiology – the study of micro-organisms such as viruses and bacteria.

Botany: rose, wheat. Zoology: cat, fish. Microbiology: bacterium, virus.

Biology is a very large subject. By dividing it into a number of fields and sub-fields, its study becomes convenient. Each field studies one part, such as plants (botany) or animals (zoology), in detail.

Microbiology, because a virus is a micro-organism, and botany, because the tomato is a plant and the damage is seen in its leaves.

Morphology is the study of the size, shape and structure of organisms; e.g. the roots, stem, leaves, flowers and fruits of a flowering plant, or the dental structure of humans.

Anatomy is the study of the internal structure of organisms (internal morphology); e.g. the muscles, heart, brain and kidneys of the human body.

Embryology: study of the development of an organism from a fertilized egg; e.g. growth of a frog from egg to embryo.

Taxonomy: classification and naming of organisms; e.g. humans are mammals and have the scientific name Homo sapiens.

Histology is the microscopic study of tissues, e.g. epithelial tissue that covers the body surface. Cytology (cell biology) is the study of the structure and functions of the cell, e.g. a plant cell or an animal cell. Histology deals with groups of cells (tissues); cytology deals with the cell.

Pathology is the study and diagnosis of diseases. Immunology is the study of the ability of the body to protect itself from foreign substances and infectious microbes, e.g. protection from polio by vaccination.

Fossils are remains of living things preserved by natural process. Their study helps us to understand the life of the past and the history of life on Earth. The branch is palaeontology.

(a) Anatomy – internal structure. (b) Pharmacology – study of drugs. (c) Ecology – relation of organisms with their environment.

(i) Study of immunity (body protection from foreign substances and infectious microbes). (ii) Taxonomy. (iii) Study of organisms that live in the sea, e.g. fish, whales and sponges.

(i) Study of genes and heredity. (ii) Palaeontology. (iii) Study of the interrelationship of organisms and their environment (environmental biology).

(a) Immunology (vaccines protect the body) – and pharmacology if the drug effect is studied. (b) Morphology, because it studies the shape, size and structure of the flower.

Biophysics: study of biological phenomena according to the principles and laws of physics, e.g. movement of muscles and bones like levers.

Biochemistry: study of chemical constituents of organisms and the chemical reactions in them, e.g. digestion, respiration and photosynthesis.

Biostatistics (biometry): collection of biological data through observations and experiments and analysing them by statistical rules. Biogeography: study of the distribution of plants and animals in the different geographical regions of the world.

Biotechnology is the use of different techniques to manipulate living organisms for the benefit of mankind (e.g. bacteria made to produce insulin). Bio-economics is the study of biology from an economic point of view (e.g. production of wheat, fish and rice and their export value).

(1) Living organisms consist of carbon, hydrogen, oxygen, nitrogen and other elements. (2) Chemical reactions such as digestion, respiration and photosynthesis take place in organisms. The physical structure of atoms and molecules decides their chemical properties and their roles in cells, so biochemistry links the two sciences.

The field is computational biology. It uses data analysis, mathematical modelling and computer simulations to understand biological systems, so it links biology with computer science and mathematics.

(a) Biophysics. (b) Bio-economics. (c) Biogeography.

Medicine is the diagnosis and treatment of different diseases. Surgery is the branch which treats diseases by removal or replacement of the defective parts or organs. MBBS stands for Bachelor of Medicine and Bachelor of Surgery.

Farming is the growing of crops and animals to provide food, wool and other products. Agriculture is the science of improving farming methods; the practice of agriculture is farming. Careers in agriculture include food science, agricultural engineering and agricultural entomology.

Fisheries is the sector concerned with fish; it contributes significantly to the economy of Pakistan. Careers include fish farming, fishery management and related research.

Biotechnology: bacteriology, virology and molecular genetics. Forestry: forest ecology and environmental engineering.

Bilal: horticulture (art of gardening); plant breeding. Rabia: animal husbandry; veterinary science, animal breeding and animal training.

The natural sciences study nature and include physics, chemistry and biology; biology is the part concerned with life. A career example is medicine: it uses the study of the human body and diseases.

Biology teaches how the body works (physiology), how germs cause diseases (pathology) and how vaccination protects us (immunology). It also teaches about food, drugs and mosquito-borne diseases like malaria and dengue. With this knowledge we can choose a healthy diet, keep clean surroundings and avoid disease.

When researchers from different fields work together to create new scientific knowledge, it is called interdisciplinary research collaboration. Examples: cognitive science (neurology, psychology, anthropology, linguistics etc.) and public health (medicine, sociology and psychology).

Scientists from all around the world team up to share ideas and knowledge and to critique each other's ideas to make progress. Example: the International Space Station, where space agencies of Europe, the USA, Russia and Japan work together.

Bioinformaticians apply computer skills in solving problems of life science. Biomedical engineers develop new devices and equipment for improving human health. (Also: astrobiologists study the effects of outer space on living organisms; cryobiologists study the effects of low temperature.)

Each person has different knowledge: biology of the germ, computer analysis of data and medical treatment. They share and critique ideas to create new knowledge. This working together of different fields is interdisciplinary research collaboration.

Qualitative observations are based on a quality or characteristic, e.g. the colour of a flower. Quantitative observations are based on a measurable value, e.g. the height of a plant in cm. Quantitative observations are expressed in numbers and are more accurate.

Qualitative: colour of cat, shape of leaves, climate of desert, song of a bird. Quantitative: height of giraffe, weight of mango fruits, body temperature of birds, volume of blood in humans, speed of tiger.

Deductions are the logical consequences of the hypothesis. They use "if … then" logic, taking the hypothesis as true. Example: If Plasmodium is the cause of malaria, then all persons ill with malaria should have Plasmodium in their blood.

The control group is treated like the experimental group except for the factor tested, so the effect of that factor can be compared. In the malaria study the blood of 100 healthy persons (control) was examined with the blood of 100 patients.

The incubation period is the time between the entry of the parasite into the host and the appearance of symptoms. The 7 healthy persons had Plasmodium in the incubation period, so they showed no symptoms, but after a few days they became ill with malaria. So the results still supported the hypothesis.

(a) King listed 20 observations in 1883 about the spread of malaria and suggested that mosquitoes transmit Plasmodium. (b) Ross (1897) allowed a female Anopheles to bite a malarial patient and found Plasmodium multiplying in its stomach; he also showed with sparrows and Culex that mosquitoes transmit bird malaria. (c) Laveran in 1882 suggested that Plasmodium is the cause of malaria.

Yes, it can be wrong, because a hypothesis is only a tentative explanation that must be tested; the fame of the scientist does not make it true. Deduction: if vaccination reduces the severity of complications, then vaccinated persons who get infected should have milder symptoms than unvaccinated persons.

(1) Female mosquitoes (vectors) breed in marshy and stagnant water, which is found in many places, so it is hard to destroy all of them. (2) Plasmodium can stay in the blood of persons in the incubation period without symptoms, so such persons can unknowingly keep the cycle going. (The textbook gives no key; these are reasoned answers.)

(i) A vector is a transmitter: an organism that carries a parasite and transfers it from one organism to another. (ii) Anopheles in man; Culex in birds. (iii) To test whether mosquitoes get Plasmodium from patients and transmit it to healthy individuals, i.e. whether mosquito spreads malaria.

Malaria is a serious and often fatal disease, so it would be unsafe and unethical to infect a healthy person on purpose. Ross therefore used sparrows in his experiments.

The first step is to recognise the biological problem and make observations: to ask "which factors (temperature, pH, amount of enzyme) change the activity of salivary amylase?" From these observations a hypothesis is then formed, deductions drawn and an experiment designed.

The other 4 persons may be in the incubation period of the disease: the virus is in the body but symptoms have not yet appeared. They may become ill after some time.

Ratio: 25 out of 40. For 160 sparrows: 25/40 × 160 = 100. About 100 sparrows are expected to get malaria.

1. Recognition: does fertilizer help bean plants to grow? 2. Observation: plants in fertilized soil look greener/taller. 3. Hypothesis: fertilizer increases the growth of bean plants. 4. Deduction: if fertilizer increases growth, then plants given fertilizer will be taller than plants without it. 5. Experiment: two groups of equal seeds, same soil, water and light; one group with fertilizer (experimental) and one without (control); measure height after 30 days.

• A hypothesis is a tentative answer to a question; a theory is a broad explanation.
• A hypothesis is narrower; a theory is much broader in scope.
• A hypothesis has little supporting evidence; a theory is supported by much more evidence.
• A theory may be modified or rejected if new results do not fit.

A scientific law is a statement that describes an observable occurrence in nature that appears to always be true. A theory that has been verified and has wide application may become a law; e.g. Mendel's law of inheritance.

When a new research method gives results that do not fit the theory, scientists must modify or even reject it, because science follows evidence.

(a) Hypothesis (tentative idea tested later). (b) Law. (c) Theory.

• It should be a general statement.
• It should be a tentative idea.
• It should agree with the available observations.
• It should be testable and potentially falsifiable.

A scientific hypothesis is only a tentative explanation. It must be testable by experiments and potentially falsifiable. Personal certainty is not evidence; only experimental results can show whether it is correct.

Molecular biology is the study of biology at the molecular level (the molecules such as DNA and proteins that run life).

Significance: it helps to understand how genes work and to make medicines and tests.

Physiology is the study of the functions of various organs of organisms, e.g. digestion, respiration, excretion, photosynthesis.

Significance: it helps us to know how the body works and to keep it healthy.

Palaeontology is the study of the history of life on Earth as based on fossils.

Significance: it helps to understand the life of the past and how living things changed.

Pharmacology is the study of drugs; a drug is a chemical substance, e.g. aspirin, insulin, penicillin.

Significance: it helps to make safe and effective medicines.

Morphology studies the size, shape and structure of organisms (external, e.g. roots, stem, leaves, dental structure); anatomy studies the internal structure (muscles, heart, brain, kidneys). Anatomy is also called internal morphology.

Cytology is the study of the structure and functions of the cell (cell biology). Genetics is the study of genes and heredity; e.g. white cats produce white kittens.

Biotechnology is the use of techniques to manipulate living organisms for the benefit of mankind (e.g. making insulin in bacteria). Immunology is the study of the immunity of the body against foreign substances and infectious microbes (e.g. vaccines for polio, corona, dengue).

Marine biology is the study of organisms that live in the sea (fish, whales, dolphins, sponges, molluscs). Ecology is the study of the relationship of organisms with their environment (e.g. pond, lake, forest, desert); it is also called environmental biology.

A hypothesis is a tentative answer to a biological problem; a tentative explanation of the observations that might be true.

• It should be a general statement.
• It should be a tentative idea.
• It should agree with the available observations.
• It should be testable and potentially falsifiable.

(a) Green leaves – physiology (and botany): leaves make food by photosynthesis, which is a function of the plant. (b) Heredity – genetics: the study of genes and how features pass from parents to offspring.

Horticulture is the art of gardening; careers include plant breeding. Animal husbandry is the care and breeding of domestic animals; careers include veterinary science, animal breeding and animal training.

The collected data are organised in tables and graphs and analysed by ratio and proportion. Analysis shows whether the results agree with the predictions (deductions) of the hypothesis, so the hypothesis is accepted, modified or rejected. Without data analysis a hypothesis cannot be judged.

Pharmacology – the study of drugs (chemical substances like aspirin and penicillin). Cytology (cell biology) – the study of the structure and functions of the cell. (Check: the paper text as recorded shows cytology twice; both rows are answered.)

A theory is a broad explanation of some aspect of the natural world based on facts repeatedly confirmed by observation and experiments, e.g. the theory that Plasmodium is the cause of malaria. A law is a statement that describes an observable occurrence in nature that always appears to be true, e.g. Mendel's law of inheritance.

Pathology – study and diagnosis of diseases. Histology – microscopic study of tissues. Paleontology – the study of the history of life on Earth based on fossils.

Horticulture is the art of gardening, e.g. growing flowers and fruit plants and plant breeding. Animal husbandry is the care and breeding of domestic animals, e.g. rearing cattle, goats and poultry; veterinary science is a career in it.

(i) Botany – plants. (ii) Taxonomy – classification and naming of organisms. (iii) Entomology – insects (a branch of zoology).

Any two: Medicine and surgery – diagnosis and treatment of diseases (MBBS). Agriculture – science of improving farming. Fisheries – fish farming and management. Forestry – planting and caring for forests. Biotechnology – bacteriology, virology, molecular genetics.

Recognition of the biological problem → Observation → Building up a hypothesis → Drawing deductions (→ Devising experiment → Inferring result).

Biology is the study of living organisms (bios = life, logos = study). It explains how living things relate to one another and to their surroundings.

Any two: medicine and surgery (diagnosis and treatment of diseases), agriculture (science of improving farming methods), animal husbandry (care and breeding of animals), fisheries (fish farming), horticulture (gardening and plant breeding) and forestry (caring for forests).

Any three: Physics – limbs move like levers (biophysics). Chemistry – digestion and respiration are chemical reactions (biochemistry). Statistics – analysing biological data (biostatistics). Geography – distribution of organisms (biogeography). Economics – production and export of wheat, rice and fish (bio-economics).

Ratio of sparrows that got malaria = 32/50. Out of 200 sparrows: 32/50 × 200 = 128 sparrows.

1. It is testable by observation or experiment.
2. It is falsifiable – it can be shown wrong by evidence.
3. It is based on observations / prior knowledge.
4. It is clear, simple and specific (and can make predictions).

In 1883 A.F.A. King observed (any three):

1. Malaria is common in marshy, swampy, low-lying damp areas and near stagnant water.
2. People living near such places, especially in warm humid weather, suffer more; it is rare where mosquitoes are absent.
3. Malaria is more often contracted at night (when mosquitoes bite); sleeping in upper floors or under nets/smoke reduces risk.
4. Drying up/draining swamps reduces malaria.

He concluded that mosquitoes spread malaria (a hypothesis later tested).

Biology is integrated with other sciences (a diagram of biology in the centre with physics, chemistry, statistics, geography, technology and economics around it). Biophysics: biological organisms work on the principles of physics, e.g. muscles and bones. Biochemistry: chemical constituents and reactions of organisms. Biostatistics (biometry): collection and analysis of biological data. Computational biology: data analysis, mathematical models and computer simulations. Biogeography: distribution of organisms. Biotechnology: use of techniques on living organisms for mankind. Bio-economics: biology from an economic point of view, e.g. production and export of wheat, rice and fish.

Steps: recognition of a biological problem; observation and identification (qualitative and quantitative); building up a hypothesis (tentative, general, testable, agrees with observations); drawing deductions (if … then); devising experiments (control and experimental groups); inferring the result (data arranged to draw results). Application: the malaria study. Problem: cause of malaria; observations about marshes, quinine and Plasmodium in blood; hypothesis of Laveran; deduction that all patients have Plasmodium; experiment on 100 patients and 100 healthy persons; result almost all patients showed Plasmodium, so the hypothesis was supported.

1. Recognition: does fertilizer help bean plants grow better?
2. Observation: plants near a fertilized field look taller (qualitative); measure height (quantitative).
3. Hypothesis: fertilizer increases the growth of bean plants.
4. Deduction: if fertilizer increases growth, then plants given fertilizer will be taller than plants without it.
5. Experiment: 20 pots, same seeds, soil, water, sunlight; 10 pots with fertilizer (experimental), 10 without (control); measure height after 30 days.
6. Results: record in a table, calculate averages; if fertilized plants are taller, hypothesis supported.

• Physics: limbs act as levers; biophysics.
• Chemistry: digestion, respiration and photosynthesis are chemical reactions; biochemistry.
• Statistics: analysis of biological data; biostatistics.
• Geography: distribution of animals such as markhor in regions; biogeography.
• Economics: production and export of wheat, rice and fish; bio-economics.
• Technology: insulin made from bacteria; biotechnology.