THE LIVING WORLD – PART 1

INTRODUCTION

living – plants, animals and microbes

characteristics of living organisms

  • Growth
  • Reproduction
  • Metabolism
  • Consciousness
  • Cellular organisation

GROWTH

Increase in mass and no. of cells individuals are twin characteristics of living things

INTRINSIC GROWTHEXTRINSIC GROWTH
occurs from inside (living)occurs from outside (non-living things)
increase in mass e.g. living thingsreversible e.g – mountains

IMPORTANT POINTS

In plants, growth occurs throughout life span

in animals – up to certain age

In unicellular organisms – Growth & reproduction are mutually inclusive events

In all living organisms’ growth occurs by cell division

growth is not a defining property, but intrinsic growth is defining property.

in multicellular organisms, growth and reproduction – exclusive events

REPRODUCTION

producing similar kind of individuals is known as reproduction

exceptions are mule, worker bees (female), sterile human couples.

reproduction is not defining property.

ASEXUAL SEXUAL
Single parent is involved two parents
occurs with or without involvement of gamete formation involve formation and fusion of gametes

Binary fission – unicellular, bacteria, amoeba

Budding – hydra

Fragmentation – spirogyra (filamentous algae), fungi, protonema of bryophytes

True regeneration – planaria(flatworm)

METABOLISM

all living organisms made up of cell

made up of thousands of chemicals and molecules

shows thousands of chemical reactions

metabolism is the sum total of chemical reactions occurring simultaneously in living organisms

ANABOLISM (endergonic) CATABOLISM (exergonic)
simple – complex complex – simple
e.g. – photosynthesis
CO2 + H20 = glucose
e.g. – respiration
glucose = CO2 + H2O + ATP

it is defining property

Isolated metabolic reactions performed in a test tube are neither living nor non-living

isolated metabolic reactions occurring in vitro (in lab) are not living thing/system but surely a living reaction

CONSCIOUSNESS

Ability to sense the surroundings and respond to environmental stimulus which may be physical, chemical or biological.

some plants like – soyabean, radish and some animal like – horse, sheep, goat are seasonal breeders and reproduce at specific season.

Reproductive behavior changes by the effect of photoperiod.

so, photoperiod effects reproduction

NOTE- only humans are self-consciousness

sense surrounding and memorize the event

due to complex brain

hence absent in coma lying person – Patient lying in hospital in comma.

CELLULAR ORGANISATION

all living organisms are made up of cells.

it is defining property.

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