Core Themes in Biology

Evolution

Evolution refers to the biological change of species over time, often due to changes in habitat. This process enables species to adapt to different environments.

• Definition: Evolution is the process by which populations of organisms change genetically over generations.

• Example: The development of antibiotic resistance in bacteria.

Organization

Organization in biology describes how living structures are arranged to perform specific functions.

• Key Point: Biological organization ranges from molecules to cells, tissues, organs, organisms, populations, communities, ecosystems, and the biosphere.

• Example: The heart is an organ made of tissues, which are made of cells.

Information

Information in biology refers to the genetic instructions carried by DNA that determine traits.

• Key Point: DNA encodes the information necessary for building and maintaining an organism.

• Example: The gene for eye color is a segment of DNA that determines pigment production.

Energy and Matter

This theme describes how energy flows through ecosystems and how matter cycles between organisms and their environment.

• Key Point: Energy flows from the sun to plants (photosynthesis), then to animals (consumption).

• Example: Carbon cycles between the atmosphere, plants, and animals.

Interactions

Interactions refer to how organisms affect each other and their environments.

• Key Point: Interactions can be competitive, cooperative, or predatory.

• Example: Bees pollinate flowers, benefiting both species.

Signs of Life

Living things share several key characteristics that distinguish them from non-living matter.

• Living things contain nucleic acids, proteins, carbohydrates, and lipids.

• Living things are composed of cells.

• Living things reproduce.

• Living things use energy and raw materials.

• Living things respond to stimuli.

• Living things maintain homeostasis.

• Populations of living things evolve and have adaptive traits.

Levels of Biological Organization

Biosphere

The biosphere encompasses all regions of Earth that support life.

• Example: Oceans, forests, and deserts are all part of the biosphere.

Ecosystem

An ecosystem consists of living things and their environment working together.

• Example: A pond ecosystem includes fish, plants, water, air, and soil.

Community

A community is all the different living things in one ecosystem.

• Example: Plants, animals, and bacteria in a meadow.

Population

A population is a group of the same species in an area.

• Example: All deer in a forest.

Organism

An organism is a single living thing.

• Example: A deer, a tree, or a bacterium.

Organ

An organ is a body part that performs a specific job.

• Example: The heart pumps blood.

Tissue

Tissues are groups of similar cells working together.

• Example: Skin tissue protects the body.

Cell

The cell is the smallest unit of life, like a tiny building block of all living things.

• Example: Muscle cells contract to produce movement.

Biological Molecules and Cells

Molecule

Molecules are super tiny particles made of atoms, such as chlorophyll, which helps plants use sunlight.

• Example: Water (H2O), DNA, and proteins are biological molecules.

Emergent Properties

Emergent properties arise from the arrangement and interactions of parts as complexity increases.

• Example: Photosynthesis requires a specific organization of molecules in the chloroplast.

Photosynthesis

Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to produce food (sugar) and oxygen.

• Chloroplast: The part inside a plant cell where photosynthesis happens. It contains chlorophyll, the green pigment that captures sunlight.

• Equation:

Cell Structure and Function

Cells are the smallest units of life that can perform all activities required for living.

• Cell Theory: All living organisms are made of cells; the cell is the basic unit of life.

• Cell Functions: Movement, energy use, response to stimuli, and reproduction.

• Shared Features: All cells are enclosed by a membrane that controls what enters and leaves.

Types of Cells

• Prokaryotic Cells: Found in bacteria and archaea; lack membrane-bound organelles.

• Eukaryotic Cells: Found in plants, animals, fungi, and protists; have membrane-bound organelles (nucleus, chloroplast); more complex and larger.

Theme: Life's Processes Involve the Expression and Transmission of Genetic Information

Genetic Information in Cells

Chromosomes within cells contain genetic material in the form of DNA (deoxyribonucleic acid). DNA encodes the instructions for building all molecules synthesized within a cell, establishing the cell's identity and function.

• Chromosome: Each contains one very long DNA molecule with hundreds or thousands of genes.

• Gene: A section of DNA that encodes a specific protein or function.

• Inheritance: Genetic information is transmitted from parents to offspring.

DNA Structure and Function

The molecular structure of DNA allows it to store information. DNA consists of two long chains (strands) arranged in a double helix, made up of four types of chemical building blocks called nucleotides: A, T, C, and G.

• Double Helix: The shape of DNA, with two strands wound around each other.

• Nucleotide: The basic unit of DNA, consisting of a sugar, phosphate, and a nitrogenous base (A, T, C, or G).

Genetic Code and Protein Synthesis

Specific sequences of nucleotides encode the information in genes. The genetic code is analogous to a four-letter alphabet. Genes provide the blueprint for making proteins, which are major players in building and maintaining the cell.

• Example: A bacterial gene may specify an enzyme to break down sugar; a human gene may specify an antibody to fight infection.

• Protein-Encoding Genes: Control protein production indirectly, using RNA as an intermediary.

• Transcription: DNA is transcribed into mRNA.

• Translation: mRNA is translated into amino acids, forming a protein.

• Equation:

Gene Expression and Universality

All forms of life use essentially the same genetic code. Differences between organisms reflect differences in nucleotide sequences, not in the code itself. This universality is strong evidence that all life is related.

• Comparative Genomics: Comparing DNA sequences between species provides information about evolutionary relationships.

• RNA: Not all RNAs code for proteins; some are components of protein-making machinery or regulate protein-coding genes.

Genomics: Large-Scale Analysis of DNA Sequences

Genome and Genomics

The genome is the complete set of genetic material in an organism. Genomics is the study of entire genomes, while proteomics studies entire sets of proteins.

• Human Genome: A typical human cell has two similar sets of chromosomes, each with about 3 billion nucleotide pairs.

• Genome Sequencing: Since the 1990s, genome sequencing has advanced rapidly, allowing the study of many species.

Key Developments in Genomics

• High-throughput technology: Enables rapid analysis of many samples.

• Bioinformatics: Uses computational tools to store and analyze large datasets.

• Interdisciplinary research teams: Scientists from many fields collaborate to advance genomics.

Summary Table: Types of Cells

Summary Table: Levels of Biological Organization

Additional info: Some explanations and examples have been expanded for clarity and completeness.