#SHORT NOTES NEET PREPARATION (Chapter 1) – LIVING WORLD (“LIVING”)
DEFINITION AND EXPLANATION
Biology – science of life forms and living processes
Living world – contain diversity (different) of living organisms.
Early man can differentiate between inanimate matter and living organisms. Inanimate matter: example – wind, sea, fire etc) and Living organisms: example – animals and plants.
Common feature of inanimate and living organisms – sense of awe or fear that they evoked.
Systematic and monumental description of life –
- detailed systems of identification, nomenclature and classification
- sharing of similarities among living organism both horizontally and vertically
Classification of animals and plants – based on taxonomist’s perspective
Features of living organisms – growth, reproduction, ability to sense environment, suitable response, metabolism, ability to self-replicate, self-organize, and interact and emergence.
Living organisms – grow (increase in mass and increase in number of individuals. Multi-cellular organism grows by cell division.
In plants – growth by cell division occurs continuously and in animals – growth is seen only up to certain age
Cell division occurs in certain tissues to replace lost cells. Unicellular organisms grow by cell division.
Increase in body mass is considered growth. Non-living objects is growing by increase in body mass as a criterion for growth (mountains, boulders and sand mounds)
Non-living objects growth is by accumulation of material on the surface. Living organisms – growth is from inside.
Reproduction – characteristics of living organisms. In multi-cellular organisms, reproduction refers to the production of progeny (sexual)
Asexual reproduction – fungi multiply and spread easily due to millions of asexual spores they produce
Lower organisms (yeast and hydra) – reproduction by budding
In planaria (flat worms), true regeneration occurs (fragmented organism regenerates the lost part of its body and becomes a new organism)
Fungi, filamentous algae and protonema of mosses – multiply by fragmentation
Unicellular organisms (bacteria, unicellular algae or amoeba) – reproduction is synonymous with growth (increase in number of cells)
Characteristics of life – metabolism
Living organisms – made of chemicals. Chemicals has various classes, sizes and functions – it is made and change into some other bio-molecules = this conversion are called chemical reactions or metabolic reactions.
Thousands of metabolic reactions occurring simultaneously inside all living organism (both unicellular and multi-cellular)
Metabolism occur – plants, animals, fungi and microbes
Metabolism – chemical reactions occur in our body
Cellular organization of the body – defining feature of life forms
Feature of living organisms – ability to sense their surroundings or environment and respond to environmental stimuli (physical, chemical or biological)
Human sense environment by sense organs
Plants respond to external factors (light, water, temperature, other organisms, pollutants)
Photoperiod affects reproduction in seasonal breeders (both plants and animals)
Consciousness – defining property of living organisms