Biology: Characteristics of Life

• Biology studies life through its structure, function, growth, origin, evolution, distribution, and taxonomy.
• Biology includes botany, zoology, microbiology, genetics, and ecology.

Characteristics of Life

• Living organisms are distinct from non-living matter through organization, metabolism, growth, adaptation, response to stimuli, reproduction, and homeostasis.
• Organization is the hierarchical structuring of living things, from cells to organ systems.
• Metabolism encompasses all chemical reactions in an organism including energy production and molecular synthesis.
• Growth signifies an increase in size and complexity through cell division and differentiation.
• Adaptation allows organisms to evolve traits that improve survival and reproduction in specific environments.
• Response to stimuli is the detection of and reaction to environmental changes like light, temperature, or chemicals.
• Reproduction is the production of new organisms, sexually or asexually.
• Homeostasis is maintaining a stable internal environment despite external changes.

Cell Biology

• The cell, the basic unit of life, executes all life processes.
• The two main cell types are prokaryotic and eukaryotic.
• Prokaryotic cells lack a nucleus and membrane-bound organelles; eukaryotic cells contain these.
• Key cell structures: plasma membrane, cytoplasm, nucleus (in eukaryotes), ribosomes, and organelles like mitochondria, chloroplasts (in plants), and endoplasmic reticulum.
• The plasma membrane regulates substance movement into and out of the cell.
• Cytoplasm is the gel-like substance housing organelles.
• The nucleus contains DNA and controls cell activities.
• Ribosomes synthesize proteins.
• Mitochondria are sites of cellular respiration for energy production.
• Chloroplasts (in plants) facilitate photosynthesis, converting light energy to chemical energy.
• The endoplasmic reticulum synthesizes proteins and lipids.

Genetics

• Genetics is the study of heredity and variation in living organisms.
• Genes, composed of DNA, are the basic units of heredity.
• DNA, a double helix, contains the genetic code.
• The genetic code dictates how DNA information translates into proteins.
• Genes reside on chromosomes within the nucleus.
• During cell division, chromosomes duplicate and pass to daughter cells.
• Mutations, changes in DNA sequence, cause trait variation.
• Inheritance patterns depend on parental gene transmission to offspring.
• Gregor Mendel's pea plant experiments established him as the father of modern genetics.
• Mendel's laws include segregation and independent assortment.
• The law of segregation: each individual has two alleles per trait, separating during gamete formation.
• The law of independent assortment: alleles for different traits are inherited independently.

Evolution

• Evolution is how populations change over time.
• Natural selection, where advantageous traits increase survival and reproduction, drives evolution.
• Charles Darwin's "On the Origin of Species" detailed evolution by natural selection.
• Fossil records, comparative anatomy, embryology, and molecular biology support evolution.
• Fossils document past life forms and their changes.
• Comparative anatomy compares organism structures to reveal evolutionary relationships.
• Embryology studies organism development, showing common ancestry through developmental similarities.
• Molecular biology compares DNA and protein sequences to determine evolutionary relationships.
• Speciation, the rise of new species, often occurs via reproductive isolation and genetic divergence.

Ecology

• Ecology studies interactions between organisms and their environment.
• An ecosystem includes living organisms and non-living components like air, water, and soil.
• Populations are groups of the same species in the same area.
• Communities are groups of different populations in the same area.
• Food chains and webs illustrate energy and nutrient flow in ecosystems.
• Producers, like plants, use photosynthesis to convert sunlight into chemical energy.
• Consumers, like animals, gain energy by consuming other organisms.
• Decomposers, like bacteria and fungi, recycle nutrients from dead organisms.
• Biomes are large ecosystems defined by specific climate and dominant plant communities.
• The biosphere is the sum of all Earth's ecosystems.
• Ecological interactions: competition, predation, mutualism, and parasitism.
• Competition is when two or more organisms need the same limited resource.
• Predation is when a predator kills and eats prey.
• Mutualism is a mutually beneficial relationship between two organisms.
• Parasitism benefits one organism (the parasite) while harming the other (the host).