Introduction to Biology

Biology Overview

• Biology is the scientific study of life, exploring the structure, function, growth, origin, evolution, and distribution of living organisms.
• The cell is recognized as the basic unit of life.
• Genes serve as the basic unit of heredity.
• Evolution is the driving force behind the creation and extinction of species.
• Homeostasis is essential for the survival of living organisms.

Branches of Biology

• Biochemistry studies the chemical processes within and relating to living organisms.
• Botany studies plants, including their physiology, structure, genetics, ecology, distribution, classification, and economic importance.
• Cell Biology studies the structure, function, and behavior of cells.
• Ecology studies the interactions of organisms with one another and with their environment.
• Evolutionary Biology studies the evolutionary processes that produced the diversity of life on Earth.
• Genetics studies heredity and variation in organisms.
• Microbiology studies microorganisms, including bacteria, archaea, viruses, fungi, and protozoa.
• Molecular Biology studies the molecular basis of biological activity between biomolecules in the various systems of a cell.
• Physiology studies the normal functions of living organisms and their parts.
• Zoology studies animals, including their behavior, physiology, structure, classification, and distribution.

Characteristics of Life

• Living things exhibit complex organization, from atoms to molecules to organelles to cells to tissues to organs to organ systems to organisms.
• Living organisms carry out chemical reactions to obtain and use energy via metabolism.
• Growth involves an increase in size or cell number.
• Reproduction enables living things to produce offspring, either sexually or asexually.
• Living things respond to stimuli by reacting to changes in their environment.
• Adaptation allows living things to evolve traits enabling them to survive and reproduce in their environment.
• Homeostasis allows living things to maintain a stable internal environment.

Cell Structure and Function

• The cell is the basic unit of life.
• Cells are either prokaryotic or eukaryotic.
• Prokaryotic cells lack a nucleus and other membrane-bound organelles, examples include Bacteria and Archaea.
• Eukaryotic cells have a nucleus and other membrane-bound organelles, examples include Eukarya (protists, fungi, plants, and animals).
• Key cell structures include the cell membrane, cytoplasm, nucleus, ribosomes, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles.

Cell Membrane

• The cell membrane is a selectively permeable barrier that surrounds the cell.
• The cell membrane regulates the movement of substances in and out of the cell.
• It consists of a phospholipid bilayer with embedded proteins.

Cytoplasm

• The cytoplasm is the gel-like substance inside the cell that contains the organelles.

Nucleus

• The nucleus is the control center of the cell as it contains the DNA.

Ribosomes

• Ribosomes are responsible for protein synthesis.

Mitochondria

• Mitochondria are the powerhouses of the cell and produce energy through cellular respiration.

Endoplasmic Reticulum (ER)

• The endoplasmic reticulum is a network of membranes involved in protein and lipid synthesis.
• There are two types of ER: rough ER (with ribosomes) and smooth ER (without ribosomes).

Golgi Apparatus

• The Golgi apparatus modifies, sorts, and packages proteins and lipids.

Lysosomes

• Lysosomes contain enzymes that break down cellular waste and debris.

Vacuoles

• Vacuoles store water, nutrients, and waste products.

Cell Cycle

• The cell cycle is the series of events in a cell leading to its division.
• The cell cycle includes duplication of its DNA through replication.
• The result of the cell cycle is two new daughter cells through division.
• The cell cycle consists of interphase and mitosis/meiosis.

Interphase

• Interphase is the period of the cell cycle during which the cell grows and duplicates its DNA.
• It consists of three phases: G1, S, and G2.

Mitosis

• Mitosis is the process of cell division that produces two identical daughter cells.
• It consists of four phases: prophase, metaphase, anaphase, and telophase.

Meiosis

• Meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell.
• It occurs in two steps, meiosis I and meiosis II.

Genetics

• The study of heredity and variation in organisms.
• Genes are the basic units of heredity and are made of DNA.
• DNA (deoxyribonucleic acid) is a molecule that carries the genetic instructions for all living organisms.
• Chromosomes are structures within cells that contain DNA.
• Humans have 23 pairs of chromosomes, for a total of 46.

Gene Expression

• The process by which genetic information is used to synthesize functional gene products (proteins).
• Involves transcription and translation.

Transcription

• The process of copying DNA into RNA (ribonucleic acid).

Translation

• The process of using RNA to synthesize proteins.

Mutation

• A change in the DNA sequence.
• Mutations can be harmful, beneficial, or neutral.

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations.
• Natural selection is the mechanism by which evolution occurs.

Natural Selection

• Natural selection allows organisms with traits that better enable them to adapt to their environment to survive and reproduce in greater numbers than others.
• Natural selection ensures the perpetuation of these favorable traits in succeeding generations.
• Natural selection results in adaptation.

Ecology

• The study of the interactions of organisms with one another and with their environment.

Ecosystem

• A community of living organisms (biotic factors) interacting with their physical environment (abiotic factors).

Population

• A group of individuals of the same species living in the same area.

Community

• A group of interacting populations in the same area.

Food Chain

• A series of organisms in which each organism eats the one below it.

Food Web

• A network of interconnected food chains in an ecosystem.

Trophic Levels

• The position an organism occupies in a food chain.
• Producers (autotrophs), consumers (heterotrophs), and decomposers.

Biodiversity

• The variety of life in the world or in a particular habitat or ecosystem.
• Biodiversity is important for ecosystem stability and resilience.

Conservation Biology

• The study of the conservation of nature and of Earth's biodiversity
• It aims to protect species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions.

Important Biological energyMolecules

• Carbohydrates provide energy and structural support.
• Lipids store energy, form cell membranes, and act as hormones.
• Proteins perform a wide variety of functions, including catalyzing reactions, transporting molecules, and providing structural support.
• Nucleic acids store and transmit genetic information (DNA and RNA).