This document provides an overview of organisms and populations. It discusses key concepts in ecology like habitat, niche, biotic and abiotic factors. Specific biotic factors covered include temperature, light, water, soil, wind and humidity. Different biomes are described like tundra, taiga, grasslands, alpine, tropical forests, temperate forests, and deserts. The document also discusses how organisms respond to abiotic factors through regulating, conforming, migrating, or suspending activities. Finally, it covers structural, behavioral and physiological adaptations that help organisms survive in different environments.

1. Chapter 10
Organisms and Population
P S MUTHUMALAR
PG ASST
KSR M H S S
TIRUCHENGODE

2. Organisms and Population

3. INTRODUCTION
ECOLOGY
The word ‘ecology’ is derived from the Greek term
‘oikos’, meaning ‘house’ and logos, meaning ‘study
The study of the environmental ‘house’ includes all
the organisms in it and all the functional processes
that make the house habitable.

4. HABITAT
A habitat can be considered as the ‘address’
of the organism
In a xerophytic habitat, the camel is able to use water
efficiently and effectively for evaporative cooling through their
skin and respiratory system.
They excrete highly concentrated urine and can also withstand
dehydration up to 25% of the body weight.
The hoofs and hump are also suitable adaptations for survival
in this dry sandy environment.

5. HABITAT
In an aquatic media, maintaining homeostasis and
osmotic balance is a challenge.
marine animals have appropriate adaptations to prevent
cell shrinkage.
While freshwater organisms have suitable adaptations to
withstand bursting of their cells.
Fish have a wide range of adaptations like fins (locomotion),
streamlined body (aerodynamic), lateral line system (sensory),
gills (respiration), air sacs (floatation) and kidneys (excretion).

6. NICHE OR ECOLOGICAL NICHE
The physical space occupied by an organism and
its functional role in the community.
Charles Elton (1927) was the first to use the term
‘niche’ as the functional status of an organism in
its community.
Groups of species with comparable role and niche
dimensions within a community are termed ‘guilds’.
Species that occupy the same niche in different
geographical regions, are termed ‘ecological
equivalents’

7. NICHE
Cricket
Grass hopper

8. NICHE

9. ABIOTIC FACTORS
TEMPERATURE
It influences all forms of life by affecting many vital activities
of organisms like metabolism, behavior, reproduction,
development and even death in the Biosphere.
The minimum and maximum temperature of an environment
regulates the survival of a cell
The metabolism of organisms is regulated by enzymes which are
temperature sensitive.
In many organisms, determination of sex and sex ratio,
maturation of gonads, gametogenesis and reproduction is
influenced by temperature.

10. VANT HOFF’S RULE
With the increase of every 10ºC, the rate of metabolic
activity doubles (or ) the reaction rate is halved with the
decrease of 10ºC
The effect of temperature on the rate of reaction is
expressed in terms of temperature coefficient or Q10 value
The Q10 values are estimated taking the ratio between the
rate of reaction at XºC and rate of reaction at (X-10ºC)
In the living system the Q10 value is about 2.0

11. Bergmann’s Rule
Birds and mammals attain greater body size in
colder regions than warmer regions

12. Allen’s Rule
Warm blooded animals, living in colder climates, tend to have
shorter limbs, ears and other appendages when compared to
the members of the same species in warmer climates

13. Jordon’s Rule
In some aquatic environments, an inverse
relationship between water temperature
and fish meristic characters is observed -
lower the temperature, more the
vertebrae

14. Adaptations to temperature
EURYTHERMS
Organisms which can survive a wide range of
temperature
(cat, dog, tiger, human)
Those organisms which can tolerate only a
narrow range of temperature
(Fish, Frogs, Lizards and Snakes)
STENOTHERMS

15. Adaptations to temperature
Organisms have adapted by forming heat resistant spores,
cysts (Entamoeba), antifreeze proteins (Arctic fishes)
 Hibernation (winter sleep)
 Aestivation (Summer sleep)
In certain conditions, migration is an appropriate
adaptation to overcome extreme temperatures

16. Adaptations to temperature

17. LIGHT
Light influences growth, pigmentation, migration and
reproduction
Induce gene mutations
Diapause
Gonads of birds become more active with increasing
light

18. LIGHT
Positive phototaxis Negative phototaxis

19. LIGHT
Phototropism

20. LIGHT
Photokinesis

21. WATER
ESSENTIAL PROPERTIES OF WATER
o Pedogenesis
o Medium – eco system
o Present – atmosphere, outer layer of lithosphere
o Heavier than air
o Float organism in a variable level
o Thermo stable
o Physically unique
o Surface of the body will freeze
o Universal solvent
o Water has high surface tension
Thermal zones of cold water bodies

22. SOIL
PEDOSPHERE

23. SOIL
Four Main functions
 Medium for plant growth
 Means for water storage and purification
 Modifier of earth’s atmosphere
 Habitat for many organisms, which in turn modify the soil
Soil is formed of many horizontal layers called
as “Soil Profile”

24. PROPERTIES OF THE SOIL
1. Texture of soil
SAND SILT
CLAY

25. PROPERTIES OF THE SOIL
2. Porosity

26. PROPERTIES OF THE SOIL
3. Permeability

27. PROPERTIES OF THE SOIL
4. Soil temperature

28. PROPERTIES OF THE SOIL
5. Soil water

29. WIND

30. WIND
Uses
ANEMOMETER

31. HUMIDITY
Moisture in the form of invisible
vapor in the atmosphere is called
humidity.
Absolute humidity
Relative humidity (or)
Specific humidity.
HYDROMETER

32. ALTITUDE

33. ACCLIMATIZATION

34. BIOMES
Biomes are large regions of earth
that have similar or common
vegetation and climatic conditions

35. BIOMES
BIOMEDISTRIBUTION

36. BIOMES
CLASSIFICATION

37. BIOMES
Characters of a Biome
 Location, Geographical position
(Latitude, Longitude)
 Climate and physiochemical
environment
 Predominant plant and animal life
 Boundaries between biomes are not
always sharply defined.
 Transition or transient zones are
seen as in case of grassland and
forest biomes

38. Aquatic Biomes
Freshwater (Lakes, ponds, rivers)

39. Aquatic Biomes
Brackish water (Estuaries / Wetlands)

40. Aquatic Biomes
Marine (Coral reefs, pelagic zones and abyssal zones)

41. Terrestrial biome

42. TUNDRA BIOME

43. TUNDRA BIOME
 This is the almost treeless plain in the
northern parts of Asia, Europe and North
America.
 Winters are long with little daylight,
Summers are short, with long daylight
hours.
 Precipitation is less than 250 mm per
year. It is a zone of permafrost.

44. TUNDRA BIOME
 Extremely cold climate
 Low biotic diversity
 Simple vegetation structure
 Limitation of drainage
 Short season of growth and
reproduction
 Energy and nutrients in the form of
dead organic material
 Large population oscillations

45. TUNDRA BIOME
Birches
Dwarf willow

46. TUNDRA BIOME
mosses sedges

47. TUNDRA BIOME
reindeer
Arctic hare

48. TUNDRA BIOME
Musk ox lemming
Arctic fox Arctic wolf
bobcat
Snowy owl

49. TAIGA BIOMES
 The Taiga is 1300-1450 km wide zone south of the
Tundra
 This area has long and cold winters
 Summer temperature ranges from 10⁰ C to 21⁰ C
 Precipitation ranges about 380-1000 mm annually

50. TAIGA BIOMES
spruce
fir
pine

51. TAIGA BIOMES
moose elk
Moose and reindeer migrate to the
Taiga for winter and to the Tundra for
summers
Pine marten

52. GRASSLAND BIOME

53. GRASSLAND BIOME
 Grasslands occur in temperate and in the
tropical regions.
 They have hot summers, cold winters, and
irregular rainfall.
 Often they are characterized by high winds.
 The low irregular rainfall is the factor which
makes the difference between a temperate
deciduous forest and a temperate grassland.

54. GRASSLAND BIOME
Jack Rabbit Prairie dog
coyotes Gaur

55. GRASSLAND BIOME
Purple needle grass
Wild oats Foxtail
Ryegrass Buffalo grass

56. ALPINE BIOME

57. ALPINE BIOME
Phacelia
Bristle cone pine
Moss campian

58. ALPINE BIOME
Polylepis Pygmy bitterroot
Wild potato

59. Tropical forest
 Near equator
 Distinct season
 20̊̊c – 25c
 Rainfall 2000mm
 Heavy leaching soil
 Penetration of light – low
 Flora is highly diverse

60. Tropical forest
Types:
1. Evergreen rain forest
2. Seasonal rain forest
3. Semi evergreen forest
4. Moist / dry deciduous forest (monsoon)

61. Tropical forest

62. Temperate forest
 North America, northeastern Asia and
western and central Europe
 Moderate climate & growing season of
140 – 200 days
 -30̊̊c - 30c
 750 – 1500mm rainfall
 Moderately dense & allow light
 3-4 tree species / sq.km

63. Temperate forest
Based on seasonal distribution of rainfall, the
types of temperate forests are:
 Moist conifer and evergreen broad-leaved
forests
 Dry conifer forests
 Mediterranean forests
 Temperate coniferous forests
 Temperate broad-leaved rainforests

64. Temperate forest

65. DESERT BIOMES
 One fifth of earth
 Very low rain fall
 Soil – Good drainage & no surface water
 Mean temperature – (20-25c)
 Extreme – (43.5 – 49c)
 Minimum - (-18c)
 Sahara, Thar desert
Types:
Hot desert
Cold desert

66. HOT DESERT
Soils often have abundant nutrients
Only animals which can tap available water
or capable of storing sufficient water and
withstand the heat can survive in the desert

67. HOTDESERT

68. COLD DESERT
Cold deserts are characterized by cold winters with
snowfall and high overall rainfall throughout the
winter and occasionally over the summer
 Antarctic, Greenland and the Nearctic
realm, parts of USA and in parts of western
Asia and the Ladakh region in India
 Mean temperature is between -2° C and 4°
C and the mean summer temperature is
between 21° C and 26° C.
 Rainfall 150- 250 mm

69. COLD DESERT

71. Responses To Abiotic Factors

72. Types of responses
1. Regulate – able to maintain homeostasis by
physiological means
2. Conform – body temperature changes with
the ambient temperature
3. Migrate – stressful habitat to a new,
hospitable area & return when the period
over
4. Suspend - inactive

73. Types of responses

74. Types of responses

75. Types of responses

76. Types of responses
Suspend

77. Adaptations
Adaptation is a dynamic
evolutionary process that fits
organisms to their environment and
enhancing their evolutionary fitness
a) Structural
b) Behavioural
c) Physiological

78. Adaptations
a) Structural adaptations
The external and internal structures of animals can help
them to adapt better to their environment

79. Adaptations
b) Behavioural adaptations
Animals develop certain behavioural traits or adaptations
for survival
Two most characteristic forms of behavioral adaptations
are migration and courtship

80. Adaptations
c) Physiological adaptations
These are adaptations of organisms that help them to live
and survive in their environment with unique niches
The two most well-known physiological adaptations are
hibernation and aestivation

81. Adaptations
Adaptations of aquatic animals
 Fins and dorsal fins act as stabilizers or balancers
 Myotomes help in locomotion
 Stream lined structure helps in the swift movement
 Respiration by gills
 Presence of lateral-line system
 Mucous glands are protected by scales
 Maintain water and ionic balance

82. Adaptations
Adaptations of terrestrial animals
 Earth worms and Planarians - maintain a moist situation
 Arthropods - external covering over the respiratory
surfaces and well-developed tracheal systems
 Vertebrate skin – prevent water loss
 Some animal - food as partial replacement of water lost
through excretion
 Birds - during drought birds rarely reproduce
 Camel - regulate water effectively for evaporative cooling
through the skin and respiratory system and excrete highly
concentrated urine, and can also withstand dehydration up to
25% of their body weight

83. Populations
Population is defined as any group of
organisms of the same species which can
interbreed among themselves, and occupy a
particular space and function as part of a
biotic community

84. Population Attributes
1. Population Density
2. Natality
3. Mortality
4. Population
Dispersion
5. Migration
6. Emigration
7. Immigration

85. Population density
The density of a population refers to its size in relation to
unit of space and time. Population density is the total
number of that species within a natural habitat.

86. Natality
Natality is equivalent to birth rate and is an
expression of the production of new
individuals in the population by birth,
hatching, germination (or) fission.
The two main aspects of reproduction, namely
fertility and fecundity play a significant role in a
population

87. Mortality
Mortality can be expressed as a loss of
individuals in unit time or death rate
Mortality is the population decline factor
and is opposite to natality

88. Mortality
Mortality rates vary among species and are
correlated and influenced by a number of factors
such as destruction of nests, eggs or young by
storms, wind, floods, predators, accidents and
desertion by parents

89. Population Dispersion
Populations have a tendency to disperse or spread out
in all directions, until some barriers are reached
Migration
Migration is a peculiar and unique kind of mass
population movement from one place to another
and back

90. Migration
Siberian crane Vedanthangal

91. Migration
Sea to freshwater
Example :salmon
Freshwater to sea
Example : Eel

92. Emigration
This is regarded as an adaptive behavior that regulates
the population in a particular site and prevents over
exploitation of the habitat
Immigration
If the population increases beyond the carrying
capacity, it can result in increased mortality among
the immigrants or decreased reproductive capacity of
the individuals

93. Population Attributes

94. Population Age Distribution
Proportion of the age groups determines the
reproductive status of the population at the
given time and is an indicator of the future
population size
Age distribution pyramids

95. Growth Models / Curves
Populations show characteristic growth patterns or
forms. These patterns can be plotted and termed as
J-shaped growth form and S-shaped growth form
(Sigmoid form)

96. Differences between r- selected and K
selected species
r selected species K selected species
Smaller sized Larger sized
Produce many offspring Produce few offspring
Mature early Late maturity with extended
parental care
Short life Long life
reproduces only once or few
times in their life time
Can reproduce more than
once in lifetime
Only few reach adulthood Most individuals reach
maximum life span
Unstable environment,
density independent
Stable environment, density
dependent

97. Population Regulation
Once the carrying capacity of the environment is reached,
population numbers remain static
(or)
fluctuate depending on environmental conditions
Density independent – Extrinsic factors
Density dependent - Intrinsic factors

98. Population Regulation

99. Population Interaction
Organisms belonging to different populations interact for
food, shelter, mating or for other necessities
intra specific - interaction within the members of same species
(or)
inter specific - among organisms of different species
Inter specific associations or interactions can be:
1. Neutral
2. Positive
3. Negative

100. Population Interaction

101. Population Interaction

102. Population Interaction

103. Population Interaction

104. Population Interaction

105. Population Interaction

106. Population Interaction