Introduction
In the study of ecology, understanding the interactions between organisms and their environment is crucial. This document will cover the key concepts of species, communities, and ecosystems as outlined in the International Baccalaureate (IB) Biology syllabus. We will delve into definitions, interactions, and examples to provide a comprehensive understanding of these ecological concepts.
4.1.1 Species & Population
Species
A species is defined as:
- A group of organisms that can interbreed to produce fertile offspring.
Key Points:
- The ability to breed and produce fertile offspring is a primary method of distinguishing species, particularly for organisms that reproduce sexually.
- For organisms that reproduce asexually (e.g., bacteria), this definition is less applicable.
- Occasionally, animals of different species can breed and produce fertile offspring, such as the "wholphin" (a hybrid between a melon-headed whale and a common bottlenose dolphin).
The melon-headed whale is actually a species of dolphin, making the name "wholphin" somewhat misleading.
Population
A population is defined as:
- A group of organisms of the same species living in an area at one time.
Key Points:
- Populations can be isolated from each other due to geographical barriers, leading to limited gene flow between them.
- If isolated populations experience different environmental pressures, natural selection can lead to speciation.
- Genetic drift can also contribute to speciation.
For instance, the Galápagos finches have evolved into different species due to isolation and varying environmental conditions on different islands.
4.1.2 Methods of Nutrition
Organisms obtain nutrients through various methods, which can be broadly classified into autotrophic and heterotrophic nutrition.
Autotrophic Nutrition
- Autotrophs: Organisms that produce their own food from inorganic substances.
- Photoautotrophs: Use sunlight to synthesize food (e.g., plants, algae).
- Chemoautotrophs: Use chemical reactions to synthesize food (e.g., certain bacteria).
Heterotrophic Nutrition
- Heterotrophs: Organisms that obtain food by consuming other organisms.
- Herbivores: Eat plants (e.g., cows).
- Carnivores: Eat animals (e.g., lions).
- Omnivores: Eat both plants and animals (e.g., humans).
- Detritivores: Consume decomposing organic matter (e.g., earthworms).
- Saprotrophs: Decompose organic matter externally and absorb nutrients (e.g., fungi).
Remember, autotrophs are the primary producers in an ecosystem, forming the base of the food chain.
4.1.3 Community
Community
A community is defined as:
- Multiple populations of different species living and interacting in the same area.
