Key Concepts in Biology

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 (e.g., bacteria) - lack a nucleus and membrane-bound organelles.
- Eukaryotic (e.g., plant and animal cells) - have a nucleus and organelles.
Organelles:
- Nucleus: contains DNA.
- Mitochondria: powerhouse of the cell, produces ATP.
- Ribosomes: protein synthesis.
- Endoplasmic reticulum (ER): protein and lipid synthesis; rough ER has ribosomes, smooth ER does not.

DNA Structure: Double helix made of nucleotides (A, T, C, G).
Gene: A segment of DNA that codes for a protein.
Chromosomes: Structures made of DNA and proteins; humans have 46 chromosomes (23 pairs).
Mendelian Genetics: Principles of inheritance; dominant and recessive traits.

Ecosystems: Interactions between living organisms and their environment.
Food Chains/Webs: Energy flow through ecosystems; producers (plants), consumers (herbivores, carnivores), decomposers.
Biomes: Large ecological areas (e.g., forests, deserts) defined by climate and vegetation.

Homeostasis: Maintenance of stable internal conditions despite external changes.
Organ Systems:
- Circulatory system: transports nutrients and oxygen.
- Respiratory system: gas exchange (O2 and CO2).
- Digestive system: breakdown and absorption of food.

Bacteria: Single-celled prokaryotes, can be beneficial (gut flora) or pathogenic (disease-causing).
Viruses: Non-cellular, require a host to reproduce.
Fungi: Eukaryotic organisms, play key roles in decomposition.

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 for photosynthesis.

These key areas provide a foundational understanding of biology and its diverse subfields.

Cell Theory states that all living organisms are made up of cells, cells are the fundamental unit of life, and new cells originate from existing cells.
Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have a nucleus and various organelles.
Nucleus contains DNA, which holds the genetic information of the cell.
Mitochondria are responsible for generating energy (ATP) for the cell, making them the powerhouses of the cell.
Ribosomes are involved in protein synthesis, crucial for cell function.
Endoplasmic reticulum (ER) can be smooth or rough. Rough ER has ribosomes attached and plays a role in protein synthesis, lipid synthesis, and detoxification. Smooth ER lacks ribosomes and focuses on lipid synthesis, detoxification, and steroid hormone production.

DNA is a double helix structure composed of nucleotide bases, adenine (A), thymine (T), cytosine (C), and guanine (G).
Genes are segments of DNA that code for specific proteins.
Chromosomes are structures made up of DNA and proteins. Humans have 46 chromosomes, organized into 23 pairs.
Mendelian Genetics describes the principles of inheritance, including dominant and recessive traits.

Natural Selection is a key mechanism of evolution where organisms with traits that increase their survival and reproduction in a particular environment are more likely to pass those traits on to the next generation.
Speciation refers to the formation of new species through evolutionary processes.
Fossil Record provides evidence of past life and shows changes in species over time, supporting the concept of evolution.

Ecosystems involve the interactions between living organisms and their non-living environment, creating a complex web of relationships.
Food Chains/Webs illustrate the flow of energy through an ecosystem. Producers, like plants, convert sunlight into energy. Consumers, like herbivores and carnivores, obtain energy by consuming other organisms. Decomposers break down dead organisms and waste, recycling nutrients.
Biomes are large-scale ecological areas characterized by specific climate patterns and distinct plant and animal communities, such as forests, deserts, and grasslands.

Homeostasis is the maintenance of stable internal conditions within an organism, despite external changes, ensuring proper function.
Organ Systems are groups of organs that work together to perform specific functions.
Circulatory System is responsible for transporting 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 into smaller molecules that can be absorbed by the body.

Bacteria are single-celled prokaryotes, playing diverse roles, including beneficial gut flora and pathogenic disease-causing strains.
Viruses are non-cellular entities requiring a host cell for replication.
Fungi are eukaryotic organisms that decompose organic matter, playing crucial roles in nutrient cycling.

Photosynthesis is the process by which plants convert light energy into chemical energy (glucose), using chlorophyll.
Roots absorb water and nutrients from the soil.
Stems provide support for the plant and transport materials between roots and leaves.
Leaves are the primary site for photosynthesis in plants.

Innate Behaviors are instinctual and genetically programmed, such as reflexes.
Learned Behaviors are acquired through experience, such as conditioning.
Social Behavior involves interactions between individuals of the same species, including cooperation, competition, and communication.

Genetic Engineering involves the modification of an organism's DNA to alter its characteristics.
CRISPR is a revolutionary tool for precise editing of genes, with significant potential in medicine, agriculture, and other fields.
Applications of biotechnology include gene therapy for treating genetic disorders and the development of genetically modified crops (GMOs) for increased yields and disease resistance.