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INTRODUCTION TO BIOLOGY

CONTENT:

  1. Meaning of (a) Science and (b) Biology
  2. Scientific method
  3. Experimental pattern
  4. Living And Non Living things
  5. Differences between plants and animals
  6. Levels of organization
  7. Complexity in multicellular organisms

 

MEANING OF SCIENCE AND BIOLOGY

Science can be defined as a systematic process of making inquiry about the living and non-living things in our environment. Science is both an organized body of knowledge and a process of finding out knowledge.

Biology is the branch of science that studies living things. The word ‘biology’ is derived from two Greek words: ‘bios’ which means life, and ‘logos’ which means study. Biology therefore means the study of life or of living things.

Biology has several branches, these include

  1. Botany (study of plants)
  2. Zoology (study of animals)
  3. Morphology (study of the external features of living things)
  4. Anatomy (study of internal structure of living things)
  5. Physiology (Study of how living things function)
  6. Ecology (study of the relationships between living things and their environment),
  7. Genetics (Study of how living things inherit characters from their parents) etc.

The prime purpose of science is research, i.e. finding out about things, so biology involves finding out or making inquiry about living things, their interaction with themselves and with nature.

 

EVALUATION

  1. Define the terms (a) Science (b) Biology
  2. State five branches of biology.
  3. Of what use is (a) science (b) biology to man?

 

METHOD OF SCIENCE

The method of science involves systematically making inquiries about something under study. It begins with observation (that is, looking at something carefully with a view to finding an answer to a question). This involves using all the senses i.e. sight, hearing, touch, feeling, pressure, taste, etc. and instruments (e.g. ruler, microscope, magnifying lens, weighing balance, telescopes, barometer, etc.) where necessary.

Observation is followed by a hypothesis i.e. a sensible, reasonable guess which is capable of being tested or verified.

The hypothesis is tested by an experiment. Experiments usually involve measurements/counting, as such they have to be carried out as accurately as possible. Scientific experiments have a control. The control experiment is identical with the experiment proper, but the factor to be tested is omitted. This gives the investigator a higher degree of confidence in his result and conclusion.

Results from an experiment are put together and a conclusion (inference/generalization) is made.

Other scientists may repeat the same experiment and if similar results are obtained then the generalization is accepted as a theory.

When a theory has been tested extensively, worldwide and found to be consistently true, it becomes a law e.g. the law of gravity

 

EXPERIMENTAL PATTERN

Experiments are designed to eliminate all forms of bias so as to avoid making false conclusions. To achieve this, only the factor being tested is varied, all other factors that may affect the result are kept constant. These experiments are known as controlled experiments.

While experimenting, a biologist uses processes of science such as counting, measuring, classifying, organizing data, communicating, recording and interpreting data.

In recording an experiment/ giving the account of a scientific investigation, the following pattern is used:

  1. Date of experiment
  2. Aim/purpose of experiment
  3. Apparatus/materials required
  4. Procedure/method used (including control and precautions)
  5. Observations
  6. Inference (deduction from what is already known)

In biology, experiments are carried out on living things. It may not be possible to get a sample of test population with identical organisms. This problem can be reduced by using large test samples and also repeating the experiment many times.

 

EVALUATION

  1. State and explain the processes involved in making inquiries in science?
  2. In your own words, what are the proper attitudes which should characterize a scientist?
  3. Enumerate the steps specified in giving account of a scientific investigation.
  4. How is bias taken care of in a biological investigation?

 

SUGGESTED PRACTICAL

Setting up and using of a light microscope.

Objectives of the Practical Exercise

Students should be able to

  1. Identify the parts and functions of each part of the microscope
  2. Calculate the magnification of a diagram
  3. Draw and label a light microscope (10 – 12cm long)
  4. Observe a chosen specimen using the microscope (cells of an onion bulb)

Note: Quality and Details to be graded in any required diagram

  1. Title (TL)
  2. Size (Sz)
  3. Clarity of lines (CL) – not broken, not wooly
  4. Neatness of Label (NL) – ruled guide lines, horizontal labels          `
  5. Details (DL) – depending on the diagram of the specimen

 

LIVING AND NON LIVING THINGS

Everything in the world can be classified as either a living thing or non-living thing. Living things include plants and animals (things that have life) e.g. Man, Monkey, Earthworm, Flies, Mango, Fresh okra plant, Hibiscus etc. Non-living things do not have life e.g. Stone, Water, Air, Table, etc.

 

CHARACTERISTICS OF LIVING THINGS

Some features have been found in every living thing ever studied by Biologists, these are;

Living things consist mainly of water and compounds carbon.

They are made up of one or more units called cells

They carry out seven basic life processes namely;

Movement – This is defined as the ability of an organism to change its position. It may be a total change in position of the body as in the case of animals that move their whole body from one place to another or a limited change in position as in the case of plants which can only move parts of their body (e.g. in bending). Living things move in order to look for food, shelter, mates (reproduction) and to escape from danger. Generally, most animals can walk, swim, or fly from one place to another but plants can only move parts of themselves in response to external stimuli. Movement from place to place is also referred to as Locomotion.

Nutrition – This is the ability of an organism to feed. The reason for feeding is to enable living things to live and carry out life processes like growth, respiration and reproduction. Plants manufacture their own food through the process of photosynthesis (autotrophic nutrition). Animals cannot manufacture their own food but depend directly or indirectly on plants for food (heterotrophic nutrition).

Respiration – This involves the taking in of oxygen in order to burn down (oxidize) food substances to release energy which is used to carry out all life processes. Carbondioxide is given off in the process.

Excretion – This is the removal of metabolic waste products from the body. Many chemical activities go on in an organism and produce waste. These waste products are substances which the organism does not need and which may poison it if allowed to build up in the body. The waste products of metabolism include carbondioxide, water, urea, e.t.c.

Irritability or Sensitivity – This is the ability of an organism to perceive and respond to stimuli (changes in the surrounding). Living things exhibits sensitivity in order to survive in their environment. The response is often by some form of movement. Stimuli include heat, light, pain, sounds, chemical substances, e.t.c.

Growth – This is defined as permanent increase in size and mass of an organism especially while young. Organisms also replace and repair worn or damaged parts of the body throughout life. The food eaten provides the basis of growth.

Reproduction – This is the ability of a living organism to produce young ones or offsprings. This ensures continuity of life. Reproduction occurs in two forms.

Asexual reproduction – This involves only one organism producing offsprings from itself.

Sexual reproduction – This involves two organisms coming together to produce offspring(s).

Apart from these seven basic life processes another characteristic of living things is that they all die. All living things have a definite and limited period of existence, and they pass through five basic stages of existence;

Birth →   Growth  →   Maturity  →  Decline (old age)  →  Death.

 

EVALUATION

  1. Make a list of five living things and five non-living things.
  2. Briefly discuss the characteristics of living things.

 

DIFFERENCES BETWEEN PLANTS AND ANIMALS

PLANTSANIMALS
Green plants carry out photosynthesisAnimals cannot carry out photosynthesis;
they depend on plants for their food.
Plants do not move from one place to
another and do not have organs of movement.
Animals move from one place to another
and have organs of movement. They exhibit
locomotion.
Growth is indefinite (continues throughout life)
and apical.
Growth is definite and occurs uniformly in
every part of the body. It stops when they
become adults.
Plants do not have specialized organs for
excretion, respiration and coordination.
Animals have specific organs for excretion,
respiration and coordination.
Plants are slow in response to stimuliAnimals are fast in their response to stimuli
Excess carbohydrates are stored as starchExcess carbohydrates are stored in form of
glycogen
They have many branchesThey do not have any branches

Some organisms exist which posses characteristics of both plants and animals an example is Euglena viridis. Euglena viridis is a microscopic unicellular organism, which lives in water.

The characteristics of Euglena which make it an animal are;

  1. Possession of flagellum used for movement.
  2. Possession of gullet for passage of food and which acts as a reservoir.
  3. Presence of eye spot which enables it respond to light.
  4. Possession of contractile vacuole used for excretion.
  5. Possession of pellicle which makes its body flexible.
  6. It can feed on other organisms (holozoic nutrition) in the absence of sunlight.

The plant characteristics of Euglena are;

  1. Possession of chloroplast which enables it to carry out photosynthesis.
  2. Possession of pyrenoid where starch is stored
  3. It can produce its own food (holophytic or autotrophic nutrition)

 

EVALUATION

  1. State five differences between plants and animals
  2. Mention two characteristics of Euglena that makes it (a) a plant (b) an animal

 

LEVELS OF ORGANISATION OF LIFE

The bodies of living things are highly organized. This organization occurs in levels, with the simplest structure occurring at the lowest levels (single cells) which interact to build up more complex structures (multicellular organisms).

The basic levels of organization of life in organisms are; cells, tissues, organs and systems.

Cell: This is the smallest unit of living organism. It is the first and simplest level of organization of life. Plants and animals are made up of cells. One celled organisms are called unicellular organisms. They include Amoeba, Plasmodium, Euglena, Paramecium, etc. Organisms made up of many cells are called multicellular organisms e.g man, mango, trees etc. The single celled organism can carry out all life processes on its own.

Tissues: This is a group of similar cells which come together to perform a particular function. A tissue consist of two or more different types of cells aggregating together to perform a specific function e.g. the mesophyl layer in leaves, xylem tissue in stems, muscles, blood (a liquid tissue) etc. Organisms which exist at the tissue level include the hydra, jelly fish, sponge etc.

Organ: Is a group of similar tissues which come together to perform a specific function. Examples in plants are flowers, roots, leaves, seeds, a rhizome, a corm, an onion bulb, a tuber, etc. Examples in animals are the skin, stomach, heart, brain, liver, eyes, ears, kidney, etc.

System: This is a group of functionally related organs which work together to perform specific functions. Examples in plants include the shoot system and root system. Examples in animals include the digestive, nervous, excretory and circulatory systems. Examples in plants are the transport system, shoot and root system.

 

Complex Multicellular Organisms

The climax of organization in higher living things is the aggregation of systems to form an organism. Complex multicellular organisms are composed of several organ systems which work harmoniously for the benefit of the organism. All animals from Platyhelminthes to Mammals, and all vascular plants are organized on this level.

 

Complexity of Organization In Higher Animals

As organisms acquire more layers of cells, they become complex in structure, thus there is an increase in complexity from unicellular to multicellular organism.

 

Advantages of Complexity

  1. It leads to cellular differentiation, thus groups of similar cells are differentiated to form tissues which carry out similar functions
  2. It leads to internal structural specialization in which the tissues become specialized to carry out specific functions.
  3. There is mutual interdependence between component cells i.e division of labour among the cells.
  4. Complexity makes higher organisms to be more efficient in carrying out life processes.
  5. Complexity leads to increase in size of organisms.
  6. It makes it possible for organisms to become more resistant to adverse condition within the environment.

Disadvantages of Complexity

  1. The cells lose their independence and become increasingly dependent on one another’s activities.
  2. Difficulties in acquisition of materials (such as oxygen and food materials) and removal of waste products by the millions of cells making up a multicellular organism
  3. Slower rate of diffusion of oxygen or respiratory gas to individual cells.
  4. Slower rate of expulsion of waste products from cells.
  5. Decrease in ability to regenerate
  6. Difficulties in reproduction.

 

EVALUATION

  1. Mention and explain the levels of organization of life.
  2. State three advantages and disadvantages each, of complexity
  3. Is a virus a living thing or a non-living thing? Give reasons for your answers.
  4. Describe one organism at the tissue level of organization (e.g. Hydra)

 

Lesson tags: Characteristics of living things, Differences between plants and animals, living and non-living things, meaning of science and biology, Organization of life., scientific method
Back to: BIOLOGY – SS1 > First Term
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