Introduction to Biology and Genetics

• Biology is the scientific study of life, examining the structure, function, growth, origin, evolution, and distribution of living organisms.
• It encompasses a broad range of fields, including genetics, ecology, evolutionary biology, physiology, and cell biology.

Genetics

• Genetics is the study of heredity and variation of inherited characteristics.
• Genes, composed of DNA, are the basic units of heredity and contain instructions for building and maintaining cells.
• The central dogma of molecular biology describes the flow of genetic information: DNA is transcribed into RNA, and RNA is translated into protein.
• Mendelian genetics explains inheritance patterns through principles like segregation and independent assortment.
• Modern genetics explores gene structure, function, mutation, and the mechanisms of gene expression and regulation.
• Genomics studies an organism's entire genome, focusing on interactions between genes and the environment.
• Genetic engineering involves manipulating an organism's genes for practical purposes, like creating modified crops.
• Epigenetics examines changes in gene expression that do not involve alterations to the DNA sequence itself.
• Population genetics studies the distribution and change in frequency of genes within populations.

Ecology

• Ecology is the study of the interactions between organisms and their environment, including both biotic (living) and abiotic (non-living) components.
• Ecosystems are communities of interacting organisms and their physical environment.
• Key ecological concepts include food webs, energy flow, nutrient cycles, and population dynamics.
• Different levels of ecological study include: organismal, population, community, ecosystem, and biosphere.
• Population ecology focuses on factors that affect population size, density, distribution, and growth.
• Community ecology examines the interactions between different species living in the same area, such as competition, predation, mutualism, and commensalism.
• Ecosystem ecology studies the flow of energy and cycling of nutrients through ecosystems including the role of decomposition.
• Conservation biology applies ecological principles to preserve biodiversity and manage natural resources.

Evolutionary Biology

• Evolutionary biology studies the processes of evolution, which are the changes in the heritable characteristics of biological populations over successive generations.
• Natural selection is a primary mechanism of evolution, where individuals with advantageous traits are more likely to survive and reproduce.
• Adaptation is the process by which populations become better suited to their environment through natural selection.
• Genetic drift involves random changes in allele frequencies within populations, especially in small populations.
• Mutation introduces new genetic variation into populations, providing the raw material for evolution.
• Gene flow, or migration, is the movement of genes between populations, which can introduce new alleles and increase genetic diversity.
• Speciation is the process by which new species arise from existing ones, often through reproductive isolation.
• Phylogenetics studies the evolutionary relationships between organisms, often represented in phylogenetic trees.
• Macroevolution examines large-scale evolutionary changes, such as the origin of new species and major evolutionary trends.

Physiology

• Physiology is the study of the functions and processes of living organisms and their parts.
• It examines how organisms maintain homeostasis, a stable internal environment, despite external changes.
• Key areas of physiology include:
• Cell physiology: studying the function of individual cells.
• Organ physiology: studying the function of specific organs.
• Systemic physiology: studying the interactions of organ systems.
• The nervous system controls rapid communication through electrical and chemical signals using neurons.
• The endocrine system regulates slower, more sustained processes through the release of hormones.
• The cardiovascular system transports oxygen, nutrients, and waste products throughout the body.
• The respiratory system facilitates gas exchange, taking in oxygen and releasing carbon dioxide.
• The digestive system breaks down food into smaller molecules for absorption.
• The excretory system removes waste products from the body and maintains fluid balance.
• The immune system protects the body from pathogens and other foreign invaders.

Cell Biology

• Cell biology studies the structure, function, and behavior of cells, the basic units of life.
• The cell theory states that all living organisms are composed of cells and that all cells arise from pre-existing cells.
• Cells are broadly classified as prokaryotic (lacking a nucleus) or eukaryotic (containing a nucleus).
• Key cellular structures include:
• The plasma membrane: regulates the movement of substances into and out of the cell.
• The nucleus: contains the cell's genetic material (DNA).
• The cytoplasm: the fluid-filled space within the cell where organelles are located.
• Organelles: specialized structures within the cell that perform specific functions, such as:
  • Mitochondria: produce energy through cellular respiration.
  • Ribosomes: synthesize proteins.
  • Endoplasmic reticulum (ER): synthesizes and transports proteins and lipids.
  • Golgi apparatus: processes and packages proteins.
  • Lysosomes: digest cellular waste and debris.
• Cell signaling involves communication between cells through chemical messengers.
• Cell division is the process by which cells reproduce, either through mitosis (for growth and repair) or meiosis (for sexual reproduction).
• Cell differentiation is the process by which cells become specialized for specific functions.
• Apoptosis is programmed cell death, a critical process for development and tissue homeostasis.