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Chapter Analysis
Intermediate14 pages • EnglishQuick Summary
Chapter 11 of Class 12 Biology, titled 'Organisms and Populations', explores the complex interactions among organisms and their environments, focusing on population ecology. It discusses various types of interactions such as mutualism, predation, and competition, and delves into concepts like population attributes (birth and death rates, sex ratio) and population growth patterns. The chapter also illustrates the significance of ecological relationships at different levels of biological organization.
Key Topics
- •Population Attributes
- •Population Growth
- •Interspecific Interactions
- •Mutualism and Commensalism
- •Population Ecology
- •Ecological Pyramids
- •Parasitism and Predation
- •Biotic and Abiotic Interactions
Learning Objectives
- ✓Understand the concept of population and its attributes.
- ✓Learn the types of population interactions and their ecological significance.
- ✓Comprehend the logistic and exponential growth models.
- ✓Analyze the role of different ecological factors in shaping population dynamics.
- ✓Identify types of species interactions and their outcomes.
- ✓Evaluate the ecological significance of carrying capacity in ecosystems.
Questions in Chapter
List the attributes that populations possess but not individuals.
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If a population growing exponentially doubles in size in 3 years, what is the intrinsic rate of increase (r) of the population?
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Name important defence mechanisms in plants against herbivory.
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An orchid plant is growing on the branch of a mango tree. How do you describe this interaction between the orchid and the mango tree?
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What is the ecological principle behind the biological control method of managing pest insects?
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Define population and community.
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Define the following terms and give one example for each: (a) Commensalism (b) Parasitism (c) Camouflage (d) Mutualism (e) Interspecific competition
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With the help of a suitable diagram, describe the logistic population growth curve.
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Select the statement which best explains parasitism.
Page 205
Additional Practice Questions
Explain the significance of the carrying capacity in a logistic growth model.
mediumAnswer: In a logistic growth model, the carrying capacity represents the maximum population size that an environment can sustainably support. It is the point where population growth stabilizes as resource limitations like food and space come into effect, preventing further growth.
Describe the role of predators in maintaining ecosystem stability.
hardAnswer: Predators help maintain ecosystem stability by controlling prey populations, preventing them from exceeding the carrying capacity. This helps reduce the intensity of competition among prey species and maintain species diversity.
What is mutualism, and how does it benefit the interacting species?
easyAnswer: Mutualism is an ecological interaction where both species benefit. For instance, in a mutualistic relationship between bees and flowers, bees get nectar for food, while flowers benefit from pollination.
Discuss how human activities can impact population dynamics.
mediumAnswer: Human activities like deforestation, pollution, and urbanization can alter habitats and reduce resources, leading to changes in population dynamics, including population decline or forced migration.
Explain the concept of competitive exclusion and its ecological implications.
hardAnswer: The competitive exclusion principle states that two species competing for the same resources cannot coexist indefinitely; one will outcompete the other. This leads to ecological separation, species extinction, or niche differentiation.