CBSE Class 12 Biology Organisms And Populations Notes

Download CBSE Class 12 Biology Organisms And Populations Notes in PDF format. All Revision notes for Class 12 Biology have been designed as per the latest syllabus and updated chapters given in your textbook for Biology in Standard 12. Our teachers have designed these concept notes for the benefit of Grade 12 students. You should use these chapter wise notes for revision on daily basis. These study notes can also be used for learning each chapter and its important and difficult topics or revision just before your exams to help you get better scores in upcoming examinations, You can also use Printable notes for Class 12 Biology for faster revision of difficult topics and get higher rank. After reading these notes also refer to MCQ questions for Class 12 Biology given our website

Organisms And Populations Class 12 Biology Revision Notes

Class 12 Biology students should refer to the following concepts and notes for Organisms And Populations in standard 12. These exam notes for Grade 12 Biology will be very useful for upcoming class tests and examinations and help you to score good marks

Organisms And Populations Notes Class 12 Biology

 ORGANISMS AND POPULATIONS

Ecology: It is a branch of biology which studies the interactions i) among organisms and ii) between the organism and its physical ( abiotic) environment.


Organism: Individual of a species.


Population: Population is a group of individuals of the same species which can interbreed among themselves and live in a localized area.


Biome: The largest ecological regions distinguishable by characteristic plants and animals. Eg. tundra, conifer, deciduous forest, grassland, tropical, and desert.


Alpine tundra: Alpine tundra is located on mountains throughout the world at high altitude where trees cannot grow. The growing season is approximately 180 days. The night time temperature is usually below freezing. Unlike the arctic tundra, the soil in the alpine is well drained.


Group of animals that live in Alpine tundra:

Mammals: mountain goats, sheep

Insects: beetles, grasshoppers, butterflies


Coniferous forests: Coniferous forests are made up mainly of cone-bearing or coniferous trees, such as spruces, hemlocks, pines and firs. The leaves of these trees are either small and needle-like or scale-like and most stay green all year around (evergreen). All are softwoods able to survive cold temperatures and acidic soil.


Temperate Forests: The term ‘temperate forest’ is very broad. It covers the forests found between the tropical and subtropical regions and the barren, treeless lands of the far north and extreme south.

Tropical forest: "Tropical forests" encompass the idyllic rainforest, the remote cloud forest, and the lesser-known but equally endangered dry forest, pine savanna and much, much more. They are not one ecosystem, but millions of unique ecosystems.


Deciduous forest: The average annual temperature in a deciduous forest is 50° F. The average rainfall is 30 to 60 inches a year. The deciduous forest has four distinct seasons, spring, summer, autumn, and winter. In the autumn the leaves change color. During the winter months the trees lose their leaves. 

Temperature, water, light, soil.


 Temperature

• Average temperature varies seasonally

  Organisms may be Eurythermal or Stenothermal

  Eurythermal- wide range of temperature tolerence

 Stenothermal-Narrow range of temperature tolerance 


Water

 Influences life of organisms. No life without water.

 Productivity and distribution of plants are water dependent.

 Organisms may be Euryhaline or Stenohaline.

  Euryhaline:Wide range of salinity tolerance

  Stenohaline:Narrow range of salinity tolerance. 


Light

  Photosynthesis and release of oxygen light dependent.

  Sciophytes need to use diurnal and seasonal light intensity of forage, migration and reproduction. 


Soil

  Nature and proportion of soil in a place depends on climate, weathering process and types of soil.

  Soil composition, grain size and aggregation determine percolation and water holding capacity of soil.

 Physical and chemical properties determine type of plants and Animals that survive in a habitat. 


Response of organisms to environmental condition 

class_12-biology_concept_237

 


Regulation
 Organisms maintain homeostasis achieved by physiological and behavioral means
 Thermo regulation and osmoregulation.

Conformation
 Cannot maintain constant internal Environment
 Body temperature and osmotic concentration of body changes with ambient temperature and concentration of medium.-Thermo confirmer and osmo-confirmer

Migration
 Organism moves away temporarily to another habitat in stressful condition. e.g.- Migratory birds like Siberian crane

Suspension
 Organisms suspend their metabolic activities during stressful condition
 Resume their function at the return of favorable conditions.

E.g. Hibernation (winter sleep) of Frog, Reptiles, Polar Bear etc
 Aestivation (summer sleep) in Snail and Fish.
 Seed dormancy.

Adaptation
 Morphological, physiological and behavioral changes that enable organisms to adjust to the ever changing environment .

E.g. Kangaroo rat survives in desert conditions through internal oxidation of fat, removing concentrated urine of limited quantity.
 Allen‗s rule-cold climate mammals have shorter ears and limbs to minimize heat loss.
 Polar mammals like seals have blubber to prevent heat loss.
 Burrowing habit to escape from heat
 Higher count of RBC, Hb (haemoglobin) at high altitudes.

Population attributes
 Birth Rate – Number of individuals born per thousand per year.
 Death Rate – Number of individuals die per thousand per year.
 Sex Ratio – Ratio of male-female in the population.
 Population density. - the number of individual organisms per unit area (appropriate measure – total number-sometimes difficult to determine or meaningless because 4
factors N+I-M+E are concerned w.r.t habitat concerned )

Age pyramids
 If the age distribution (per cent individuals of a given age or age group) is plotted for the population, the resulting structure is called an age pyramid.
 Three ecological ages:
 Pre-reproductive, Reproductive and Post-Reproductive
 High proportion pre-reproductive individuals occur in Expanding population
 Pre-reproductive individuals are uniform in Stable population.
 Pre-reproductive individuals are less in Declining population.

CBSE Class 12 Biology - Organisms and Populations

 

Population growth

Factors that affect the size of population
Food
availability
Weather
Predation pressure
Competition
Density of population at any time at a given
place depends on Natality, Mortality, Emigration
Immigration


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Chapter 3 Human Reproduction
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Chapter 4 Reproductive Health
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Chapter 5 Principles of Inheritance and Variation
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Chapter 6 Molecular Basis of Inheritance
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CBSE Class 12 Biology Molecular Basis Of Inheritance Notes Set A
CBSE Class 12 Biology Molecular Basis Of Inheritance Notes Set B
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Chapter 7 Evolution
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CBSE Class 12 Biology Evolution Notes Set A
CBSE Class 12 Biology Evolution Notes Set B
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Chapter 8 Human Health and Diseases
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Chapter 9 Strategies for Enhancement In Food Production
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Chapter 10 Microbes In Human Welfare
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CBSE Class 12 Biology Microbes In Human Welfare Notes Set B
Chapter 11 Biotechnology Principles and Processes
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Chapter 12 Biotechnology and Its Application
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Chapter 13 Organisms and Populations
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Chapter 14 Ecosystem
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Chapter 15 Biodiversity and Conservation
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Chapter 16 Environmental Issues
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