The study of organisms and populations is a fundamental aspect of ecology, focusing on how individual organisms interact with their environment and how populations of species change over time.
Important Highlighted Point of NCERT: Organisms and Populations
1) Various levels of biological organisation– macromolecules, cells, tissues, organs, individual organisms, population, communities, ecosystems and biomes.
2) Bulbul singing in the early morning.
3) The ‘how type’ questions seek the mechanism behind the process.
4) The “why-type” question seeks significance of the process
5) Night blooming flowers generally white.
6) Ecology is a subject that deals with the interaction among Organisms, and between organism and its physical environment.
7) Ecology concerned with four levels of biological organisation – Organisms, Populations, Communities and Homes.
8) Organisms are adapted to their environment not only for survival but also reproduction.
9) Precipitation includes both rain and snow.
10) Annual variation in precipitation formed biomes like desert, rain forest, tundra etc.
11) Extreme harsh habitats → Rajasthan desert, Meghalaya forests
12) Temperature, water, light and soil are the key elements that lead to variation.
13) Niche refers to the role or position that an organism occupies within its ecosystem.
14) Temperature is the most important ecologically relevant factor.
15) The average temperature is thermal spring, hydrothermal vents 100℃.
16) Mango trees cannot grow in Canada,Germany.
17) Tuna fish are rarely caught beyond tropical latitudes in the ocean.
18) Eurythermal organisms tolerate and thrive at a wide range of temperatures.
19) Stenothermal organisms are restricted to tolerate a narrow range of temperature.
20) Aquatic organisms face chemical composition, pH of water.
21) The salt concentration is less than 5 ppm in inland waters, 30-35 ppm in sea and >100 ppm in some hypersaline lagoons.
22) Euryhaline organisms tolerate a wide range of salinity.
28) Stenohaline organisms are restricted to tolerate a narrow range of salinity.
24) Plants dependent on sunlight for flowering “photo periodic requirement”.
25) Red, green, brown algae inhabit the sea.
26) Soil is dependent on the climate, weathering process.
27) Internal environment of species permits all biochemical reactions and physiological functions for maximal efficiency.
28) Try to maintain the constancy of its internal enviroment of organisms called homeostasis.
29) Mammals regulate thermoregulation /osmoregulation and maintain body temperature and live in Antarctica or Sahara.
30) Shiver, a kind of exercise which produces heat and raises the body temperature.
31) Thermoregulation is energetically expensive for many organisms.
32) Keolado National Park (Bharatpur) in Rajasthan hosts thousands of migratory birds coming from Siberia.
33) Bears going to hibernation during winter.
34) Snails and Fish go into aestivation to avoid summer.
35) Zooplankton species in lakes and ponds are known to enter diapause, a stage of suspended development.
36) Kangaroo rat in North America deserts is capable to meet his its water requirements through internal fat oxidation.
37) Desert plants have thick cuticles on their leaf surfaces. Stomata arranged in deep pits to minimise loss of water by transpiration.
38) CAM trees enable their stomata to remain closed during day.
39) Opuntia have no leaves – they are reduced to spines.
40) Mammals have short ears and limbs to minimise heat loss in cold climates. This is Allen’s Rule.
41) Seals have a thick layer of fat (blubber).
42) Altitude sickness is felt by high altitude places like Rohtang Pass near Manali and Leh.
43) Symptoms of altitude sickness- nausea fatigue and heart palpitation.
44) Tribes that live in high altitude have a higher red blood cell.
45) Microbes (Archaebacteria) found in hydrothermal vents where temperature is > 100°C.
46) Organisms living in such extreme environments show a fascinating array of biochemical adaptations.
47) Desert lizards lack physiological ability to deal with high temperatures unlike mammals.
48) Interbreeding implies sexual reproduction
49) Cormorants in wetlands, bacteria in culture plates and lotus plants are examples of population.
50) Population ecology is important because it links ecology of population genetics and evolution.
51) Attribute characteristic of population is sex ratio.
52) The shape of pyramids throws (i) Growing (ii) Stable (iii) Declining
53) Population size called Population density (N) measures numbers only.
54) Sc.name of carrot grass → Parthenium hysterophorus.
55) N is population density at time t, its density at time t+1 then
Nt+1 = Nt [(B+I) – (D+E)]
56) Sometimes populations in nature show restraints on growth.
57) r is called the intrinsic rate of natural increase.
58% for Norway nat tris 0.015, Hour beetle is 0.128 human 18 An
59) Population maximise reproductive fitness called Darwinian fitness.
60) Pacific Salmon fish, Bamboo breed one time.
61) Oysters, pelagic fishes produce a large number of offspring.
62) ‘+’ for beneficial. ‘-’ for detrimental and 0 for neutral interaction.
63) Conduits for energy transfers across trophic level, predators play an important role.
64) Prickly pear cactus in Australia (1920) spread rapidly millions of hectares.
65) Cactus feeding predator (moth) controls the pear cactus.
66) Rocky intertidal communities of the American Pacific Coast the Starfish Pisaster is a predator.
67) Predators in nature are prudent.
68) Monarch butterfly has a chemical in its body to distasteful for its predator (bird).
69) 25% of insects are known to be phytophagous (feed plant sap and other plant parts.).
70) Weed Calotropis growing in abandoned fields and producing cardiac glycosides.
71) The Abingdon tortoise in Galapagos Island became extinct in decade by introducing goats (greater browsing efficiency).
72) Competitive release where a species experiences reduced competition for resources when a competitor is removed or its population declines.
73) Connell’s elegant field experiments on rocky sea coasts of Scotland superior barnacle Balanus dominate the smaller barnacle Chathamalus.
74) Gause states the ‘Competitive exclusion Principle’.
75) MacArthur showed five species of warblers able to avoid competition and co-exist due to behavioural differences.
76) Parasites adapted by loss of unnecessary sense organs, suckers to cling, loss of digestive system, high reproductive capacity.
77) Human liver fluke – Fasiola hepatica (trematode parasite) depends on snails & fish.
78) Ecto parasites feed on the external surface of the host. Example- lice, copepods
79) Cuscuta is a parasitic plant that grows in a hedge of plants.
80) Endoparasites live inside of the host. Example-
81) Brood parasitism in birds is an example of parasitism in which a bird lays eggs on the host’s nest for incubation.
82) Commensalism is the interaction in which one species benefits and the other is neither harmed or benefited.
83) Orchid growing as an epiphyte on a mango branch.
84) Barnacles growing on the back of a whale.
84) Association of Cattle egret and grazing cattle is a classy example of Commensalism.
85) Sea anemone has stinging tentacles and the clown fish lives among them.
86) Lichens represent a mutualistic relationship between fungus & photosynthetic algae/ cyanobacteria.
87) Mycorrhizae are associations of fungus and roots of higher plants.
88) Plant provides energy yielding carbohydrates to fungi.
89) Fascinating example of mutualism is the plant-animal relationships. Where animals dispersed seeds and plants provide nectar or fruits.
90) Species of fig trees can be pollinated by only its partner wasp.
91) Female wasps use the fruit not only as oviposition (egg-laying) site but used developing seeds of its nourishing larvae.
92) Orchids show bewildering diversity and attract bees and bumble bees for pollination.
93) Mediterranean orchid Ophrys employs ‘sexual deceit’ to get pollination.
94) Pseudocopulates exhibit behaviour resembling copulation with flowers or other objects.
1 thought on “Organisms and Populations: NCERT Biology 12”