Introduction to BiologyLecture 1

Aspects of Science

Science has two aspects. It is both

(1) a body of knowledge and

(2) a method used for discovering new knowledge.

What is biology?

• The word biology comes from the Greek words bios, which means life, and logos, which means thought.

• Thus, biology is the science that deals with the study of life.

Importance of Biology

Biology encompasses:

a) The cellular basis of living things

b) The energy of metabolism that underlies the activities of life

c) The genetic bases for inheritance in organisms

d) It also includes the study of evolutionary relationships

amongst organisms

e) Includes the diversity of life on earth

f) It considers the biology of microorganisms, plants and animals

and it brings together the structural and functional relationships

that underlie their day to day activities.

Scopes of Biology for non major science

• Anthropology

• Biotechnology

• Food technology

• Biomedical Engineering

• Veterinary medicine

• Medicine

• Forensic Science

• Geology

• Bioinformatics

Unifying Themes of Biology

Hierarchical organization of life

• -- Structural make up, from the smallest, simple to largest,complex

Cell theory

• -- All organisms are made of cells, central idea in all studies ofbiology

Heredity

• -- Biological information is inherited from parents of onegeneration by the offspring of the next.

Evolution

• -- The modification of populations over time

Regulation

• -- To survive and reproduce, all forms of life must regulatetheir internal, and sometimes external, environment.

Structure and function

• -- Correlations between the structure of a biological object,and its function.

Environmental interactions

• -- Individuals interact with other organisms of their ownspecies and those of the greater community.

Energy flow

• -- Energy flows through a food chain, cycles through anecosystem, or is converted to different forms within the cellsof an organism.

Characteristics of Living Things

• The need for energy

• Movement

• Cellular structure and organization

• Growth and development

• Maintaining Homeostasis and Repair

• Reproduction

• Response to stimuli

• Variation and adaptation

• Metabolism

1. The Need for Energy

2. Movement

It is a characteristic of organisms that they or some part of them are capableof moving themselves. We can identify movement in living organisms atdifferent levels.

For example:

Whole organism can move: a mammal can run.

Organs inside organism can move: a heart beat, intestines move foodalong them using squeezing movements.

Individual cell can move: an amoeba can move from place to place usingPseudopodia.

In case of plant: when a leaf grows towards the sun or a flower closes atnight, the opening of buds on a tree or

One of the most interesting examples of motion in plants is shown by theMimosa pudica, commonly called the Sensitive Plant. If this plant istouched, its leaves quickly fold up.

3. Cellular Structure and Organization

• All living things are made up of cells.

• Some have only one cell; others have millions of cells.

• Some cells are very simple and others are very complex.However, from bacteria and amoebas to trees and humans,the cell is the basic unit in which substances are organized toproduce a living thing.

Protoplasm

• Living cells contain a complexmixture of substances that iscalled protoplasm.

• This mixture is found only inliving cells.

• The protoplasm itself, however, is not alive.

• None of the materials of whichprotoplasm is made carbohydrates, fats, proteins,waters, and other compounds are alive.

• Yet, living cells have the abilityto organize all these materialsinto what biologists call a livingcondition.

Organism

• Living things have the ability to organize materials intoprotoplasm and to organize protoplasm and other substancesinto cells.

• Living things are therefore called organisms because of thisability to organize substances.

4. Growth and Development

All living organisms must grow.

Living organisms grow using food that they obtain fromnutrition. The molecules are formed into new living material.

Growth is a permanent increase in body size.

Plants carry on growing all their lives.

Animals stop growing when they reach a certain size.

Eggs in incubator Chicken Cock/ Hen

Development

• The series of changes that take place as an organism growstoward its final form is called development.

• All living things undergo development.

• If you plant a bean seed, it will become a bean plant. It neverbecomes a potato plant or a tree.

• It becomes a unique living thing with specialized parts thatmake it different from other living things.

5. Maintaining Homeostasis and Repair

• Homeostasis: The maintenance of internal body temperature withrespect to the surroundings.

• Most living things live long after growth appears to have stopped.

• They may not grow any larger but they must continually maintainand repair the materials of which they are made.

• Organs involved in maintaining homeostasis include skin, liver andpancreas and kidneys.

• Skin cells on your body wear away and must be replaced by newones. A cut on your finger heals because new tissues are producedto cover the cut.

• Drinking water when thirsty, Sweating to release water duringsummer all are examples of homeostasis.

6. Reproduction

• It is a basic law of biology that only life can produce life andlike produces like. Reproduction is the process whereby allliving organisms produce offspring.

Plants make seeds that grow into new plants.

Animals lay eggs or have babies.

7. Response to Stimuli

• A stimulus sound, touch, heat, light, moisture causes aresponse by a living thing.

• All living things are able to respond to certain stimuli orchange in their environment (surroundings).

• A dog comes when you whistle. A fly moves when you try toswat it.

• A Mimosa (Sensitive) plant folds its leaves in response todarkness, touch, and heat.

Irritability

• A living thing’s response to a stimulus is called irritability.

• Irritability is valuable to animals in many ways.

• It helps them obtain food and avoid predators.

• It is most highly developed in those animals that havenervous systems and keen sense organs such as eyes, nose,and ears.

• Plants usually respond slowly to stimuli because they lacksense organs, muscles, and other parts needed for a quickresponse. However, they usually respond to light by turningtheir leaves towards it.

• Even single-celled organisms such as amoebas showirritability. Such organisms respond to touch, light, heat, andother environmental stimuli.

Coordination

• Response to stimuli must be coordinated if they are to beeffective.

• Even simple organisms have many parts and each part mustdo the right thing at the right time if the proper response is tobe carried out.

• .A system of nerves and a system of chemical regulators calledhormones coordinates these responses in many otheranimals.

• In plants, only hormones are involved in the coordination ofresponses.

Behaviour

• Organisms respond to stimuli by changing their relationship toit.

• For example, a dog usually comes when you whistle. Itchanges its location in response to the stimulus.

• Such responses, which often occur in definite pattern, arecalled behaviour.

• Remember that behaviour must begin with the organism.

• A ball rolling down a hill is not showing behaviour. It is simplybeing pulled along by the force of gravity.

8. Variation and Adaptation

Variation

• Change occurs as a result of a characteristic called variation.

• Offspring always differ in some ways from one another and from theirparents. These differences are called variations.

• Now and then a variation occurs that does give an organism a betterchance of surviving in a changing environment.

• Suppose that the climate of an area is changing and deeper snow isproduced each winter. Clearly a variation that produced longer legs ina deer would increase that deer’s chances of surviving in that area.

• If this variation is passed on to the offspring of that deer, they, also,would have an increased chance of survival. Gradually the only deer ofthat type to be found in the deep snow area may be the long-leggedtypes.

• The others would have moved away or died.

Adaptation

• The process by which a certain type of organisms becomesbetter suited to survive in its environment is calledadaptation.

• Keep in mind that organisms do not change in order to survivein a changing environment.

• The deer in our example did not grow long legs because theyneeded them to survive in the deep snow.

• Organisms do not change to survive; they survive becausethey change.

9. Metabolism

The sum of all the chemical transformations that occur in a cell ororganism in a series of enzyme-catalyzed reactions is calledmetabolism.

• It includes taking in food, or ingestion, as well as taking in water and air.

• It also includes all the changes in food materials that occur within organisms during digestion.

• It includes all changes that occur as the products of digestion are assimilated, or put together, during growth, maintenance, and repair.

• Finally, metabolism includes the release of energy through respiration.

• Finally, it includes the elimination of by-products through excretion.

It is of two types:

• Catabolism:

The degradation phase of metabolism. The catabolic pathwaysrelease free energy which is conserved in the formation of ATPreduced electron carriers like NADH or NADPH.

• Anabolism:

The biosynthetic phase of metabolism which requires the inputof energy, generally in the forms of the free energy of hydrolysisof ATP and the reducing power of NADH and NADPH.

A few important themes tie together the

diverse topics in biologyHierarchical organization

Organization levels of life

REVIEW QUESTIONS

1. What is Biology? What are the importance of Biology? 2. Write down the scopes of biology for non-major science.3. Define: Heredity, Evolution, Environment interactions, Energy flow 4. What are the characteristics of living things? Describe briefly the

characteristics.5. Describe the term growth and development in context to living organisms.6. What are irritability, coordination and behavior in living organisms?7. Describe the term variation and adaptation.