Biology: Evolution and Cell Biology

Definition: Change in the heritable characteristics of biological populations over successive generations.
Natural Selection: Process where organisms better adapted to their environment tend to survive and produce more offspring.
- Variations in traits
- Struggle for existence
- Survival of the fittest
Common Descent: Idea that all living organisms share a common ancestor.
Speciation: Formation of new and distinct species through evolution.
- Allopatric speciation (geographic separation)
- Sympatric speciation (reproductive isolation)

Cell Theory:
- All living organisms are composed of cells.
- Cells are the basic unit of life.
- All cells arise from pre-existing cells.
Types of Cells:
- Prokaryotic: Simple cells without a nucleus (e.g., bacteria).
- Eukaryotic: Complex cells with a nucleus (e.g., plant and animal cells).
Cell Structures:
- Nucleus: Contains genetic material (DNA).
- Mitochondria: Powerhouse of the cell, produces energy (ATP).
- Ribosomes: Sites of protein synthesis.
- Cell Membrane: Semi-permeable barrier that controls entry and exit of substances.

Definition: A community of living organisms interacting with their physical environment.
Components:
- Biotic: Living factors (plants, animals, microorganisms).
- Abiotic: Non-living factors (water, soil, climate).
Trophic Levels:
- Producers: Organisms that produce their own food (e.g., plants).
- Consumers: Organisms that consume other organisms (herbivores, carnivores).
- Decomposers: Break down dead organic matter (fungi, bacteria).
Energy Flow: Energy is transferred through food chains and food webs, with energy loss at each trophic level.

Definition: The variety of life in a particular habitat or ecosystem, including species diversity, genetic diversity, and ecosystem diversity.
Importance:
- Ecosystem stability and resilience.
- Provision of ecosystem services (pollination, water purification).
- Cultural and aesthetic value.
Threats:
- Habitat loss (deforestation, urbanization).
- Climate change.
- Pollution.
- Overexploitation of species.
Conservation Efforts:
- Protected areas (national parks, wildlife reserves).
- Sustainable practices (fishing, agriculture).
- Restoration ecology (rehabilitating degraded ecosystems).

Change in heritable characteristics occurs over successive generations in biological populations.
Natural selection favors organisms that adapt effectively to their environments, influencing survival and reproduction.
Key principles:
- Variations in traits lead to competition among organisms.
- Struggle for existence drives evolutionary change.
- Survival of the fittest emphasizes leading to reproductive success.
Common descent posits that all living organisms share a common ancestor, highlighting interconnectedness in life.
Speciation leads to the emergence of new species:
- Allopatric speciation occurs through geographic separation, leading to distinct evolutionary paths.
- Sympatric speciation arises from reproductive isolation within the same geographic area.

Cell theory states that:
- All living organisms consist of cells, the fundamental unit of life.
- Cells originate from pre-existing cells through division.
Types of cells:
- Prokaryotic cells are simple, lacking a nucleus (e.g., bacteria).
- Eukaryotic cells are complex, containing a nucleus (e.g., plant and animal cells).
Key cell structures include:
- Nucleus, which houses genetic material (DNA).
- Mitochondria, known as the powerhouse of the cell, generating energy in the form of ATP.
- Ribosomes, the sites where protein synthesis occurs.
- Cell membrane, a semi-permeable barrier regulating the entry and exit of substances.

An ecosystem comprises a community of living organisms interacting with their physical environment.
Components include:
- Biotic factors, which are living (e.g., plants, animals, microorganisms).
- Abiotic factors, which are non-living (e.g., water, soil, climate).
Trophic levels outline energy flow:
- Producers synthesize their own food (e.g., plants).
- Consumers rely on other organisms for food (herbivores and carnivores).
- Decomposers break down dead organic matter (e.g., fungi, bacteria).
Energy transfer within food chains and food webs represents a loss of energy at each trophic level.

Biodiversity refers to the variety of life within a habitat or ecosystem, encompassing:
- Species diversity, genetic diversity, and ecosystem diversity.
Importance of biodiversity includes:
- Enhancing ecosystem stability and resilience.
- Providing essential ecosystem services, such as pollination and water purification.
- Offering cultural and aesthetic value to communities.
Threats to biodiversity arise from:
- Habitat loss through deforestation and urban development.
- Climate change impacts on ecosystems.
- Pollution affecting air, water, and soil quality.
- Overexploitation of species leading to declines in populations.
Conservation efforts focus on:
- Establishing protected areas, such as national parks and wildlife reserves.
- Implementing sustainable practices in fishing and agriculture.
- Engaging in restoration ecology to rehabilitate degraded ecosystems.