Introduction to Biology

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What is Biology ? The study of Living Things

Bio = life logy = knowledge

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Biology – The Study of Life Life arose more than 3.5

billion years ago.

First organisms (living things) were single celled.

They were the only life on Earth for millions of years.

Organisms changed over time (evolved).

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Aristotle (384 –322 BC) Proposed the theory of spontaneous generation

Also called abiogenesis.

Idea that living things can arise from nonliving matter

Idea lasted almost 2000 years.

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Spontaneous Generation For centuries, people based their beliefs on their

interpretations of what they saw going on in the world around them without testing their ideas.

They didn’t use the scientific method to arrive at answers to their questions.

Their conclusions were based on untested observations.

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Examples of Spontaneous Generation

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Observation: Every year in the spring, the Nile River

flooded areas of Egypt along the river, leaving behind

nutrient-rich mud that enabled the people to grow that year’s crop of food.

However, along with the muddy soil, large numbers of

frogs appeared that weren’t around in drier timesConclusion: It was perfectly obvious to people back then that muddy soil gave rise to the frogs

How life began…Our planet soon after it was formed some 4500 million years ago, now seems like an alien world where no living thing could survive. The earth’s atmosphere comprised of: Little or no oxygen Toxic gases like carbon monoxide, methane and

ammonia, together with nitrogen and hydrogen. These above and dense clouds of water vapour were

blasted into the sky from numerous active volcanoes and hot springs.

The world was also exposed to UV light and intense heat from the sun, flashes of lightning during frequent violent thunderstorms, and radioactive leaking from inside the planet.

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Life’s Beginnings

The chemicals of life accumulated in lakes and ponds, where they changed, combined, and re-combined in millions of different ways over vast periods of time.

Complexity increased until cell like structures appeared with the first major characteristics of life: the ability to reproduce and grow, feeding on materials from the ‘primordial soup’ in which they formed.

About a thousand million years later, cells appeared which changed the course of evolution. They developed the green pigment chlorophyll, which enabled them to use sunlight energy to make food from water and carbon dioxide, releasing oxygen into the Earth’s atmosphere for the first time.

These, the first plants gave rise to the Plant Kingdom we know today. They not only maintain an oxygen rich atmosphere, but make the food upon which all other life depends.

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Needs of living things…Light and Carbon Dioxide:All life forms need energy to survive. Living things use energy to grow, to defend themselves, and to move around – this energy is provided by the Sun – the primary source of energy.

Plants use sunlight and carbon dioxide from the air to create their own food by photosynthesis.

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Many animals then eat the plants, taking this energy into

their own bodies. Other animals then eat these plant eaters, passing the Sun's energy from one organism to another.

The food organisms take in provides them with energy,

and also provides them with the resources, and raw materials they need to build up their bodies, grow, and repair damage.

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All organisms need substances such as nutrients, water, and gases from the environment.

The stability of the environment depends on the healthy functioning of organisms in that environment.

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WaterLiving things need water to survive. Earth are comprised entirely

of water. Your own body is about 66% water. Water in your blood helps transport food, and chemicals to the cells. helps remove waste products from the body. is used to cool down and to warm up the body to carry out the chemical reactions. Plants use water to grow, to transport food, and to carry out chemical reactions. Plants use water as part of photosynthesis, to create their own food.

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Oxygen Most life forms use oxygen as the main ingredient in many of

the chemical reactions needed for life.

Land animals breath oxygen directly from the air, while ocean bearing animals use the oxygen dissolved in the water to survive.

Minerals:

The Earth’s soil contains minerals, which are essential for health and growth.

Plants take in minerals through their roots.

Animals get minerals by eating plants and/or other animals. . 14

Warmth:

If it gets too hot or cold, the chemical changes which are necessary for life will stop.

In many parts of the Earth, temperatures lie between 25deg Celsius and 30deg Celsius.

Most living things are adapted to live at these temperatures.

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Autotrophs Organisms that make their own

food are called Autotrophs.

Phototrophs: Use solar energy (photosynthesis) to get energy.

Convert H2O and CO2 into sugar and O

Chemotrophs – use different chemical processes to get energy

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Heterotrophs Organisms that must take in food to meet

their energy needs are called Heterotrophs. Consume autotrophs (herbivores), other

heterotrophs (carnivores) or both (omnivores) for their energy needs.

Complex chemicals are broken down and reassembled into simpler chemicals needed by organisms.

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It is not always an easy thing to tell the difference between living, dead, and non-living things There a few set of rules which are

followed by scientists to classify something as living:

Living things are made of cells. Living things obtain and use energy. Living things grow and develop. Living things reproduce. Living things respond to their environment. Living things adapt to their environment. 18

Basic characteristics of living things

Nutrition Respiration Excretion Growth Reproduction Movement

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Nutrition: Take food for energy, growth and repair. Plants make their own food in their leaves by a

process called photosynthesis. Carbon dioxide + Water Glucose +

Oxygen

Animals cannot make their own food, and hence, they rely on plants, and/or other animals for their source of food.

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Respiration: It is the oxidation of food to produce energy.

Living things respire. They get energy from food by a process called respiration. This usually needs oxygen.

Food + Oxygen Energy + Waste (Water + Carbon Dioxide)

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Excretion: Removal of metabolic wastes (not feces).Living things excrete. All living things produce waste.

The removal of waste from their bodies is called

excretion.

Animals excrete through their lungs and kidneys, and through their skin, when they sweat.

Plants store waste in old leaves, which fall in the autumn. 22

Growth: Permanent increase in size and complexity.

Living things reproduce and grow. Animals lay eggs, or

have babies, whereas seeds from plants grow into new plants.

Animals stop growing when theyreach their adult size.

Plants grow all their lives.23

Movement: Animals: Whole organism moves from place to place.

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Plants: Only part of its organ can move about. Plants move by growing. They do not have sense organs but respond to the environment – roots show positive geotropism, and hydrotropism as they grow downwards in response to gravity and water, and shoots show positive phototropism in response to water.

Stability and Homeostasis Organisms must Maintain very stable

internal conditions. This process is known as Homeostasis.

Temperature, water content, chemical content, etc. must be maintained.

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Reproduction and Inheritance

Reproduction: All organisms produce new organisms like themselves. Reproduction is the production of new independent organisms which are similar to their original parents. Organisms transmit hereditary information to theiroffspring. It is called Inheritance.

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Sexual Reproduction

Hereditary information from two different organisms of the same species are combined.

Egg and sperm zygote (fertilized egg).

Zygote contains hereditary information from both parents.

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Asexual Reproduction

It is the genetic information from single parent.

Hereditary information from one, usually unicellular organism divides.

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Cells Most organisms are composed of many cells (multicellular). Cells are different (undergo differentiation). Cells are highly organized. The cell is the structural and functional unit of all living

organisms. It is the smallest unit of an organism that is classified as living, and is sometimes called the building

block of life. Our skin, muscles, brain are all made of cells. Humans have an estimated 100 trillion cells. The largest known cell is an ostrich egg.

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Cell membrane – semi permeable protection around the cell.

Cytoplasm – Jelly-like substance, containing hundreds of chemicals, where lots of chemicals reactions take place. It fills the cell.

Nucleus – it controls what a cell does, and how it develops.

Mitochondria – power house of cell. Vacuole – this is a space within the cell containing

air, liquids, or food particles. Animals cells usually have several small vacuoles.

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INSIDE AN ANIMAL CELL:

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Cell Structure and Function Cells are the basic unit of life. All organisms are made of and

develop from cells. Some are composed of only a

single cell(unicellular) which is usually identical to the parent.

They contain a set of instructions called DNA (genetic information).

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Cells are not all the same shape. There are about 20 different cells in our bodies,

which are ‘specialized’ to do different jobs.

Red blood cells: Disc shaped and their job is to carry

oxygen round the body.White blood cells: They can change their shape as

theyattack germs. They provide immunity and fight

againstdiseases.Nerve cells: Have long thin fibers, which carry

nerve impulses (messages) around the body.

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DNA (Deoxyribonucleic acid)

Genetic. Information in all cells is called Deoxyribonucleic Acid

DNA contains instructions for traits genes.

Make the structures and complex chemicals necessary for life called proteins.

DNA in every body cell (somatic cells) are exactly alike.

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INSIDE A PLANT CELL: Cell wall: Made of cellulose. It covers the cell membrane.

Cell Membrane:Semi permeable protection around the cell.

Cytoplasm:Jelly-like substance, containing hundreds of chemicals, where lots of chemicals reactions take place. It fills the cell.

Vacuole: present in all plant cells. Contains liquid called cell sap.

Chloroplasts: Tiny discs full of green substance called chlorophyll. They trap the light energy that plants need to make food by photosynthesis.

Stored food: Mainly starch.

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PLANT CELL

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