Organisms and Their Environment

Organisms and Their Environment

Every organism lives in a particular environment and interacts continuously with both biotic and abiotic components of that environment.

किसी organism का survival अकेले उसके शरीर की विशेषताओं पर depend नहीं करता। उसके आसपास का temperature, water, light, soil, other organisms और उपलब्ध resources भी उसके जीवन को प्रभावित करते हैं।

1. What is Ecology?

Ecology is the branch of biology that deals with the interactions among organisms and between organisms and their physical environment.

Ecology में यह study किया जाता है कि organisms कहाँ रहते हैं, किन environmental conditions में survive करते हैं और दूसरे organisms तथा environment के साथ कैसे interact करते हैं।

2. Levels of Biological Organisation

Ecological studies can be understood at different levels of biological organisation.

Level	Meaning
Organism	A single individual organism
Population	A group of individuals of the same species living in an area
Community	Different populations living and interacting in an area
Ecosystem	Living organisms interacting with the physical environment
Biome	A large regional ecosystem characterised by climate and vegetation
Biosphere	The global sum of all ecosystems

3. Organism and Its Environment

An organism is influenced by several environmental factors. The major abiotic factors include:

• Temperature
• Water
• Light
• Soil

Biotic factors include interactions with other living organisms.

4. Abiotic Factors

Abiotic factors are the non-living components of the environment.

उदाहरण: temperature, water, light, humidity, soil, pH and minerals.

5. Biotic Factors

Biotic factors are the living components of an ecosystem.

Examples include:

• Plants
• Animals
• Microorganisms
• Predators
• Competitors
• Parasites

6. Temperature

Temperature is one of the most important abiotic factors affecting organisms.

It influences enzyme activity, metabolism, growth, reproduction and survival.

Most organisms can survive only within a limited range of temperature.

Temperature बहुत कम या बहुत अधिक होने पर biochemical reactions प्रभावित हो सकती हैं और organism की survival क्षमता कम हो सकती है।

7. Ectotherms and Endotherms

Animals can be broadly grouped according to how their body temperature relates to environmental temperature.

Ectotherms	Endotherms
Body temperature is strongly influenced by environmental temperature.	Maintain relatively constant internal body temperature through physiological mechanisms.
Examples include most fishes, amphibians and reptiles.	Birds and mammals are examples.

8. Water

Water is essential for all living organisms because it is required for metabolic reactions and other physiological processes.

Availability of water strongly influences the distribution of organisms.

Desert organisms, aquatic organisms and organisms living in moist forests show different adaptations according to water availability.

9. Water Availability and Plants

Plants living in dry environments have adaptations that help reduce water loss.

For example, xerophytic plants may have:

• Thick cuticle
• Reduced leaves or spines
• Sunken stomata
• Extensive root systems

इन adaptations का मुख्य उद्देश्य water loss को reduce करना और available water का efficient use करना है।

10. Light

Light is particularly important for plants because it provides energy for photosynthesis.

Light also influences flowering, growth, reproduction and behaviour in many organisms.

Different organisms require different intensities and durations of light.

11. Soil

Soil provides plants with physical support, water and mineral nutrients.

Soil characteristics such as:

• pH
• Mineral composition
• Water-holding capacity
• Texture
• Organic matter

influence the distribution and growth of plants.

12. Major Responses of Organisms

When environmental conditions change, organisms may respond in different ways.

Major responses include:

• Regulation
• Conformation
• Migration
• Suspension of activity

13. Regulators

Regulators are organisms that maintain a relatively constant internal environment despite changes in external conditions.

Birds and mammals are examples of organisms that regulate their body temperature.

इस process में energy expenditure होता है क्योंकि body को internal conditions maintain करने के लिए physiological mechanisms continuously काम करने पड़ते हैं।

14. Conformers

Conformers are organisms whose internal body conditions change with the external environment.

Most animals and plants cannot maintain a constant internal environment for all physiological parameters and are therefore often described as conformers for particular conditions.

15. Regulators vs Conformers

Regulators	Conformers
Maintain relatively constant internal conditions.	Internal conditions change with external conditions.
Require energy for regulation.	Generally spend less energy on maintaining a constant internal condition.
Birds and mammals regulate body temperature.	Many ectothermic organisms conform to environmental temperature.

16. Migration

Migration is the temporary movement of organisms from one region to another to avoid unfavourable environmental conditions or to obtain better resources.

For example, many birds migrate seasonally.

Migration organisms को food availability, temperature या breeding conditions जैसी environmental changes से temporarily escape करने में मदद करती है।

17. Suspension of Activity

Some organisms reduce or suspend their metabolic activity during unfavourable conditions.

Examples include:

• Hibernation
• Aestivation
• Diapause
• Dormancy

18. Hibernation

Hibernation is a state of reduced metabolic activity during very cold conditions.

कुछ animals winter के दौरान अपनी metabolic activity, body temperature और other physiological activities को significantly reduce कर देते हैं।

19. Aestivation

Aestivation is a state of reduced metabolic activity during hot and dry conditions.

यह organisms को extreme गर्मी और water shortage से बचने में मदद करता है।

20. Diapause

Diapause is a stage of suspended development observed in some insects and other organisms under unfavourable environmental conditions.

21. Adaptation

Adaptation refers to the morphological, physiological or behavioural features that enable an organism to survive and reproduce successfully in its environment.

Adaptations long-term evolutionary processes के result हो सकते हैं और organism को particular environmental conditions में survival advantage देते हैं।

22. Adaptation in Desert Plants

Desert plants face high temperature and limited water availability.

Common adaptations include:

• Thick waxy cuticle
• Reduced leaf surface
• Leaves modified into spines in some plants
• Sunken stomata
• Deep or extensive root systems

इन adaptations से transpiration द्वारा होने वाला water loss कम किया जा सकता है।

23. Adaptation in Aquatic Organisms

Aquatic organisms show adaptations according to their water environment.

Fish have a streamlined body that reduces resistance while swimming.

Many aquatic plants have flexible stems and air-filled tissues that assist in floating and gas exchange.

24. Adaptation in Kangaroo Rat

The kangaroo rat is adapted to desert conditions and can survive with very little free water.

Its kidneys are highly efficient in conserving water.

यह example दिखाता है कि physiological adaptations भी organism को harsh environmental conditions में survive करने में मदद कर सकती हैं।

25. Acclimatisation

Acclimatisation is the adjustment of an individual organism to a change in its environment during its lifetime.

For example, humans living at high altitudes gradually undergo physiological changes that help them cope with lower oxygen availability.

26. High Altitude and Acclimatisation

At high altitudes, atmospheric pressure and oxygen availability are lower.

Humans moving to high altitudes may initially experience breathlessness, headache and nausea.

Over time, the body responds by increasing breathing rate and producing more red blood cells, which helps improve oxygen transport.

27. Adaptation vs Acclimatisation

Adaptation	Acclimatisation
Usually an evolutionary characteristic.	Adjustment occurring during an individual's lifetime.
Develops over generations.	Develops within a relatively short period.
Can involve genetic changes.	Generally involves physiological or phenotypic adjustment.

28. Population

A population is a group of individuals of the same species living in a particular geographical area and sharing or interacting within the same habitat.

Population ecology studies characteristics such as population density, birth rate, death rate, age distribution and sex ratio.

29. Population Density

Population density refers to the number of individuals of a population per unit area or volume.

The density can be represented as:

Population Density = Number of individuals / Unit area or volume

However, population density is not always expressed only as the number of individuals. Depending on the organism, biomass or percentage cover may also be used.

30. Natality

Natality is the birth rate of a population.

It represents the number of new individuals added to a population through reproduction during a given period.

31. Mortality

Mortality is the death rate of a population.

It represents the number of individuals lost from a population due to death during a given period.

32. Immigration and Emigration

Immigration is the movement of individuals into a population.

Emigration is the movement of individuals out of a population.

Process	Effect on Population
Natality	Increases population
Immigration	Increases population
Mortality	Decreases population
Emigration	Decreases population

33. Population Growth

Population size changes because of births, deaths, immigration and emigration.

The basic population change can be represented as:

Population change =
(Natality + Immigration) − (Mortality + Emigration)

यदि births और immigration की संख्या deaths और emigration से अधिक है, तो population बढ़ेगी।

34. Age Distribution

Age distribution shows the proportion of individuals belonging to different age groups in a population.

Three broad age groups are:

• Pre-reproductive
• Reproductive
• Post-reproductive

Age distribution gives important information about the future growth potential of a population.

35. Age Pyramids

An age pyramid is a graphical representation of the age distribution of a population.

It may indicate whether a population is expanding, stable or declining.

Type	General Meaning
Expanding	Large proportion of younger individuals
Stable	Relatively balanced age distribution
Declining	Smaller proportion of younger individuals

36. Sex Ratio

Sex ratio refers to the proportion or relative number of males and females in a population.

Sex ratio can influence the reproductive potential and future population growth.

37. Population Interactions

Different populations living together interact with one another.

Important interactions include:

• Predation
• Competition
• Parasitism
• Commensalism
• Mutualism

38. Predation

Predation is an interaction in which one organism, the predator, kills and consumes another organism, the prey.

Example: A tiger feeding on a deer.

Predation helps regulate prey populations and is an important ecological interaction.

39. Competition

Competition occurs when two or more organisms require the same limited resource.

Competition may occur between members of the same species or between different species.

Food, water, space, light and nutrients are common resources for which organisms may compete.

40. Parasitism

Parasitism is an interaction in which one organism, the parasite, obtains food and shelter from another organism, the host, generally causing harm to the host.

Examples include:

• Cuscuta growing on a host plant
• Tapeworm living in the human intestine
• Ticks feeding on animals

41. Commensalism

Commensalism is an interaction in which one species benefits while the other is neither significantly harmed nor benefited.

Example: Epiphytic orchids growing on trees.

Orchid को tree से support मिलता है, जबकि tree को generally कोई significant benefit या harm नहीं होता।

42. Mutualism

Mutualism is an interaction in which both species benefit.

Examples include:

• Lichen – algae and fungus
• Mycorrhiza – fungus and plant roots
• Pollination interactions between plants and animals

43. Ecological Interactions – Sign Convention

Interaction	Effect on Species 1	Effect on Species 2
Predation	+	−
Parasitism	+	−
Competition	−	−
Commensalism	+	0
Mutualism	+	+

Symbols: + = benefit, − = harm, 0 = no significant effect.

44. Important Examples

Interaction	Example
Predation	Tiger and deer
Parasitism	Cuscuta and host plant
Commensalism	Orchid and tree
Mutualism	Lichen
Mutualism	Mycorrhiza
Competition	Organisms competing for limited resources

45. Important Differences

Habitat vs Niche

Habitat	Niche
The physical place where an organism lives.	The functional role and position of an organism in its environment.
Describes where an organism lives.	Describes how an organism lives and uses resources.

46. Habitat

Habitat is the physical place or environment in which an organism lives.

Examples include pond, forest, desert, grassland and ocean.

47. Ecological Niche

Ecological niche describes the functional role of an organism in an ecosystem, including how it uses resources and interacts with other organisms and environmental conditions.

दो organisms का habitat similar हो सकता है, लेकिन उनका ecological niche अलग हो सकता है।

48. Fundamental Environmental Principle

An organism can survive only within a particular range of environmental conditions.

For any environmental factor, there may be:

• Minimum limit
• Optimum range
• Maximum limit

The range between the minimum and maximum limits is called the range of tolerance.

49. Law of Tolerance

Shelford's law of tolerance states that the existence and distribution of an organism depend upon its tolerance limits for various environmental factors.

यदि किसी environmental factor की value organism की tolerance range से बाहर चली जाए, तो organism survive नहीं कर पाएगा।

50. Important Factors Affecting Organisms

Factor	Major Effect
Temperature	Affects metabolism, growth and survival
Water	Affects physiological processes and distribution
Light	Important for photosynthesis and biological rhythms
Soil	Provides support, water and minerals
Biotic interactions	Affect survival, reproduction and population size

51. Very Short Answer Questions

1. What is ecology?
2. What are abiotic factors?
3. Name four major abiotic factors.
4. What are biotic factors?
5. What is population?
6. What is population density?
7. Define natality.
8. Define mortality.
9. What is immigration?
10. What is emigration?
11. What is adaptation?
12. What is acclimatisation?
13. What is migration?
14. Define hibernation.
15. Define aestivation.
16. What is predation?
17. What is parasitism?
18. What is mutualism?
19. What is commensalism?
20. What is ecological niche?

52. Short Answer Questions

1. Explain the role of temperature as an abiotic factor.
2. How does water availability affect the distribution of organisms?
3. Explain the importance of light for plants.
4. Differentiate between regulators and conformers.
5. Explain migration as a response to environmental conditions.
6. What is adaptation? Give suitable examples.
7. Differentiate between adaptation and acclimatisation.
8. Explain population density and its significance.
9. How do natality, mortality, immigration and emigration affect population size?
10. Explain age distribution and age pyramids.
11. Differentiate between predation and parasitism.
12. Explain commensalism with an example.
13. Explain mutualism with two examples.
14. What is ecological niche?

53. Long Answer Questions

1. Describe the major abiotic factors affecting organisms and explain their effects.
2. Explain the different responses of organisms to environmental conditions.
3. Describe the major adaptations that help organisms survive in different environments.
4. Explain population characteristics such as density, natality, mortality, immigration, emigration and age distribution.
5. Describe different types of population interactions with suitable examples.

54. Multiple Choice Questions

1. The branch of biology dealing with interactions between organisms and their environment is:

   (A) Genetics   (B) Ecology   (C) Cytology   (D) Taxonomy

   Answer: (B) Ecology

2. Which of the following is an abiotic factor?

   (A) Predator   (B) Parasite   (C) Temperature   (D) Competitor

   Answer: (C) Temperature

3. Birds and mammals are generally:

   (A) Ectotherms   (B) Endotherms   (C) Parasites   (D) Decomposers

   Answer: (B) Endotherms

4. Movement of individuals into a population is called:

   (A) Emigration   (B) Immigration   (C) Mortality   (D) Natality

   Answer: (B) Immigration

5. Movement of individuals out of a population is called:

   (A) Immigration   (B) Emigration   (C) Natality   (D) Recruitment

   Answer: (B) Emigration

6. The birth rate of a population is called:

   (A) Mortality   (B) Natality   (C) Immigration   (D) Migration

   Answer: (B) Natality

7. The death rate of a population is called:

   (A) Natality   (B) Mortality   (C) Immigration   (D) Growth

   Answer: (B) Mortality

8. In mutualism:

   (A) Both species benefit   (B) Both are harmed   (C) One benefits and other is harmed   (D) Neither benefits

   Answer: (A) Both species benefit

9. In commensalism:

   (A) Both benefit   (B) One benefits and the other is unaffected   (C) Both are harmed   (D) One is harmed and the other unaffected

   Answer: (B) One benefits and the other is unaffected

10. Which interaction is represented by (+, −)?

    (A) Mutualism   (B) Competition   (C) Predation   (D) Commensalism

    Answer: (C) Predation

11. Hibernation generally occurs during:

    (A) Very cold conditions   (B) Very wet conditions   (C) Flowering   (D) Pollination

    Answer: (A) Very cold conditions

12. Aestivation is associated with:

    (A) Hot and dry conditions   (B) Cold conditions   (C) High oxygen   (D) Pollination

    Answer: (A) Hot and dry conditions

13. Orchid growing on a tree is a common example of:

    (A) Parasitism   (B) Commensalism   (C) Predation   (D) Competition

    Answer: (B) Commensalism

14. Lichen represents:

    (A) Predation   (B) Mutualism   (C) Parasitism   (D) Competition

    Answer: (B) Mutualism

15. The functional role of an organism in an ecosystem is called its:

    (A) Habitat   (B) Niche   (C) Biome   (D) Population

    Answer: (B) Niche

55. Fill in the Blanks

1. The study of interactions between organisms and environment is called ________.
2. Temperature is an ________ factor.
3. The birth rate of a population is called ________.
4. The death rate of a population is called ________.
5. Movement into a population is called ________.
6. Movement out of a population is called ________.
7. Both species benefit in ________.
8. One species benefits and the other remains unaffected in ________.
9. One organism kills and consumes another in ________.
10. The functional role of an organism is called its ecological ________.

56. Assertion and Reason

1. Assertion: Temperature affects the distribution of organisms.

   Reason: Temperature influences metabolic and physiological processes.

   Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion.

2. Assertion: Immigration increases population size.

   Reason: Immigration adds individuals to a population.

   Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion.

3. Assertion: Mutualism benefits both interacting species.

   Reason: In mutualism, the interaction has a positive effect on both partners.

   Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion.

4. Assertion: Predation can regulate prey populations.

   Reason: Predators kill and consume prey.

   Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion.

57. Practice Set – Identify the Interaction

1. Tiger and deer → ________
2. Cuscuta and host plant → ________
3. Orchid growing on a tree → ________
4. Lichen → ________
5. Two species competing for the same limited food → ________

Answers:

1. Predation
2. Parasitism
3. Commensalism
4. Mutualism
5. Competition

58. Practice Set – Population Change

Complete the following:

1. Natality → Population ________
2. Immigration → Population ________
3. Mortality → Population ________
4. Emigration → Population ________

Answers:

1. Increases
2. Increases
3. Decreases
4. Decreases

59. Quick Revision

60. One-Line Exam Facts

• Ecology deals with interactions among organisms and between organisms and their environment.
• Temperature, water, light and soil are major abiotic factors.
• Birds and mammals are endothermic animals.
• Population size changes through natality, mortality, immigration and emigration.
• Natality and immigration increase population size.
• Mortality and emigration decrease population size.
• Age pyramids represent age distribution of a population.
• Predation is an important ecological interaction.
• Competition occurs when organisms require the same limited resource.
• Parasitism benefits the parasite and harms the host.
• Commensalism benefits one species while the other is not significantly affected.
• Mutualism benefits both interacting species.
• Lichen is an example of mutualism.
• Orchid growing on a tree is an example of commensalism.
• Cuscuta is an example of a parasitic plant.
• The place where an organism lives is its habitat.
• The functional role of an organism is its ecological niche.
• Shelford's law describes the importance of tolerance limits in determining the distribution of organisms.