Organism and population
Unveiling Nature’s Complexity: A Biologist’s Quest
Nature’s Intricate Tapestry:
- Diverse and Complex: Our living world exhibits fascinating diversity and complexity.
- Biological Organization Levels: Ranges from macromolecules to biomes.
Two Fundamental Questions:
- How and Why: Exploration involves two types of questions.
- How-Types: Seek the mechanism behind a process.
- Why-Types: Seek the significance of a process.
- How and Why: Exploration involves two types of questions.
Example Inquiry:
- Bulbul’s Morning Song: Questions may include “How does the bird sing?” (mechanism) and “Why does the bird sing?” (significance).
- Mechanism: Involves the operation of the voice box and vibrating bone.
- Significance: Related to the bird’s communication with its mate during breeding season.
- Bulbul’s Morning Song: Questions may include “How does the bird sing?” (mechanism) and “Why does the bird sing?” (significance).
Scientific Observation in Nature:
- Inquisitive Approach: Scientific observation prompts questions like:
- Night-Blooming Flowers: Why are they generally white?
- Bee’s Nectar Selection: How does a bee know which flower has nectar?
- Cactus Thorns: Why does the cactus have numerous thorns?
- Chick’s Recognition: How does a chick recognize its own mother?
- Inquisitive Approach: Scientific observation prompts questions like:
Ecology’s Focus:
- Interaction Exploration: Ecology studies interactions among organisms and with the physical environment.
- Levels of Focus: Organisms, populations, communities, and biomes.
Chapter’s Emphasis:
- Population-Level Ecology: Delving into the intricacies of ecological interactions at the population level.
Population
Exploring Population Ecology: A Collective Tale
Population Dynamics:
- Group Dynamics: Rarely do we find isolated individuals; species form populations with shared resources and potential for interbreeding.
- Population Examples: Cormorants in a wetland, rats in an abandoned dwelling, teakwood trees in a forest tract, bacteria in a culture plate, and lotus plants in a pond.
Significance of Populations:
- Natural Selection at Population Level: While individuals cope with environmental changes, natural selection operates at the population level, influencing trait evolution.
- Link to Genetics and Evolution: Population ecology connects ecology with population genetics and evolution.
Population Attributes:
- Births and Deaths: Individuals experience births and deaths, while populations have birth rates and death rates per capita.
- Sex Ratio: Populations exhibit a sex ratio (e.g., 60% females, 40% males).
- Age Distribution: Populations consist of individuals of different ages, visualized through age pyramids reflecting growth status.
Population Size and Density:
- Size and Density Definition: Population size (density) is the number of individuals in a population per unit area.
- Measuring Population Size: Can be challenging; total numbers, per cent cover, or biomass serve as meaningful measures.
- Relative Densities: Sometimes, relative densities, like the number of fish caught per trap, suffice for ecological investigations.
Indirect Estimation:
- Challenges in Direct Counting: Large or elusive populations often require indirect estimation.
- Tiger Census Example: In national parks, tiger populations are estimated through pug marks and fecal pellets.
