Cell Biology and Genetics Overview

Cell Structure: Basic unit of life; contains organelles.
- Prokaryotic Cells: Lack nucleus; smaller; e.g., bacteria.
- Eukaryotic Cells: Have nucleus; larger; e.g., animal and plant cells.
Cell Organelles:
- Nucleus: Contains genetic material (DNA).
- Mitochondria: Powerhouse; site of ATP production.
- Ribosomes: Protein synthesis.
- Endoplasmic Reticulum (ER):
  - Rough ER: Covered with ribosomes; protein synthesis.
  - Smooth ER: Lipid synthesis; detoxification.
- Golgi Apparatus: Modifies, sorts, and packages proteins.

DNA Structure: Double helix; composed of nucleotides (A, T, C, G).
Gene: Segment of DNA that codes for a protein.
Alleles: Variants of a gene; influence traits.
Mendelian Genetics:
- Dominant and recessive traits.
- Law of Segregation: Alleles separate during gamete formation.
- Law of Independent Assortment: Genes for different traits segregate independently.

Ecosystem: Community of living organisms and their environment.
Biomes: Major ecological areas (e.g., desert, rainforest).
Food Chain/Web:
- Producers: Autotrophs (plants).
- Consumers: Heterotrophs (herbivores, carnivores).
- Decomposers: Break down waste and dead organisms.
Trophic Levels: Levels in a food chain (primary producers, primary consumers, etc.).

Organ Systems:
- Circulatory System: Transports blood, nutrients, gases.
- Respiratory System: Gas exchange (O2 and CO2).
- Digestive System: Breaks down food, absorbs nutrients.
- Nervous System: Controls body responses; includes brain and spinal cord.
Homeostasis: Maintenance of stable internal conditions.

Macromolecules:
- Proteins: Made of amino acids; perform various functions.
- Carbohydrates: Sugars and starches; energy source.
- Lipids: Fats and oils; energy storage, cell membranes.
- Nucleic Acids: DNA and RNA; carry genetic information.
Enzymes: Biological catalysts that speed up chemical reactions.

Photosynthesis: Process by which plants convert sunlight into energy ( glucose).
Plant Structures:
- Roots: Absorb water and nutrients.
- Stems: Support and transport materials.
- Leaves: Main site of photosynthesis.

Animal Classification: Based on taxonomy (kingdom, phylum, class, etc.).
Animal Behavior: Study of how animals interact with each other and their environments.
Mammals: Warm-blooded; have hair or fur; produce milk for offspring.

The cell is the fundamental unit of life, containing specialized structures called organelles.
Prokaryotic cells lack a nucleus, are smaller, and include bacteria.
Eukaryotic cells have a nucleus, are larger, and include animal and plant cells.
Key organelles and their functions:
- Nucleus: Stores genetic material (DNA) and controls cell activities.
- Mitochondria: The "powerhouse" of the cell, responsible for ATP production.
- Ribosomes: Sites of protein synthesis.
- Endoplasmic Reticulum (ER):
  - Rough ER: Studded with ribosomes, involved in protein synthesis.
  - Smooth ER: Involved in lipid synthesis and detoxification.
- Golgi Apparatus: Modifies, sorts, and packages proteins for transport.

DNA, a double helix, is made up of nucleotides. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base (Adenine, Thymine, Cytosine, Guanine).
A gene is a segment of DNA that codes for a specific protein.
Alleles are alternative forms of a gene that influence traits.
Mendelian genetics, studying inherited characteristics, established two key laws:
- Law of Segregation: Alleles separate during gamete formation, ensuring each gamete receives only one allele for each trait.
- Law of Independent Assortment: Genes for different traits segregate independently from each other, leading to diverse combinations of traits.

Natural selection is the driving force behind evolutionary change. Individuals with traits that enhance survival and reproduction are more likely to pass on those traits to their offspring, leading to gradual changes in populations.
Adaptation refers to traits that enhance an organism's ability to survive and reproduce in its environment.
Speciation is the formation of new species, often occurring through isolation and accumulation of genetic differences.
Common descent states that all species on Earth are related and have diverged from common ancestors over millions of years.

An ecosystem comprises a community of living organisms (biotic factors) and their non-living environment (abiotic factors).
Biomes are large-scale ecological areas characterized by distinctive plant and animal communities, climate, and geographic location (e.g., deserts, tropical rainforests, tundra).
Food chains and food webs depict the flow of energy through an ecosystem:
- Producers: Autotrophs, like plants, convert sunlight energy into chemical energy.
- Consumers: Heterotrophs, including herbivores (eat plants) and carnivores (eat other animals), obtain energy by consuming other organisms.
- Decomposers: Break down dead organisms and waste products, releasing nutrients back into the ecosystem.
Trophic levels represent different feeding positions in a food chain, with primary producers at the base and higher levels representing consumers.

The human body is organized into organ systems, each with specialized functions:
- Circulatory System: Transports blood, nutrients, oxygen, and waste products throughout the body.
- Respiratory System: Facilitates gas exchange, taking in oxygen and releasing carbon dioxide.
- Digestive System: Breaks down food and absorbs nutrients.
- Nervous System: Controls body responses, including voluntary and involuntary movements, and processes sensory information (brain and spinal cord are key components).
Homeostasis is the maintenance of stable internal conditions, crucial for proper functioning of the body.

Bacteria: Single-celled prokaryotes, ubiquitous in nature. Some are beneficial, while others are pathogenic, causing disease.
Viruses: Acellular entities, not considered living organisms, require a host to replicate and cause disease.
Fungi: Eukaryotic organisms, including yeasts, molds, and mushrooms. Play important roles in decomposition and nutrient cycling.

Photosynthesis: Plants convert sunlight energy into chemical energy (glucose).
Plant Structures:
- Roots: Anchor plants, absorb water and nutrients from the soil.
- Stems: Support the plant, transport water and nutrients from roots to leaves.
- Leaves: The primary site of photosynthesis.

Animals are classified based on taxonomic categories (kingdom, phylum, class, order, family, genus, species).
Animal behavior studies how organisms interact with each other and their environments.
Mammals: Warm-blooded vertebrates, characterized by hair or fur, and milk production for offspring.