Core Principles of Biology

• Biology is the scientific study of life, examining the structure, function, growth, origin, evolution, distribution, and taxonomy of living organisms.
• Evolution is the change in the heritable characteristics of biological populations over successive generations.

Core Principles of Biology

• Cell theory: The cell is the basic unit of life.
• Gene theory: DNA is the fundamental hereditary material.
• Homeostasis: Living organisms maintain a stable internal environment.
• Evolution accounts for the unity and diversity of life.

Cell Theory

• All living organisms are composed of one or more cells.
• The cell is the basic unit of structure and function in organisms.
• All cells arise from pre-existing cells.

Gene Theory

• Genes, composed of DNA, are the basic units of heredity.
• Genes encode the information necessary to synthesize proteins and other essential molecules.
• Genes are passed from parents to offspring, influencing the traits of the offspring.

Homeostasis

• Organisms maintain a stable internal environment despite changes in the external environment.
• Homeostatic mechanisms involve feedback loops that regulate various physiological processes.
• Examples of homeostasis include temperature regulation, pH balance, and glucose concentration.

Evolution

• Evolution is the process by which populations of organisms change over time.
• These changes are heritable and passed on through genes.
• Evolution is driven by mechanisms such as natural selection, mutation, genetic drift, and gene flow.

Natural Selection

• Natural selection is a key mechanism of evolution.
• Individuals with traits better suited to their environment are more likely to survive and reproduce.
• These advantageous traits become more common in the population over time.

Mutation

• Mutations are changes in the DNA sequence that can introduce new traits.
• Mutations can be spontaneous or caused by environmental factors.
• Mutations provide the genetic variation upon which natural selection acts.

Genetic Drift

• Genetic drift refers to random changes in the frequency of traits in a population.
• It is more pronounced in small populations.
• Genetic drift can lead to the loss of genetic variation.

Gene Flow

• Gene flow is the movement of genes between populations.
• It can introduce new genetic variation into a population.
• Gene flow can reduce genetic differences between populations.

Evidence of Evolution

• Fossil records provide evidence of past life forms and their transitions.
• Comparative anatomy reveals similarities in the structures of different organisms.
• Molecular biology shows the relatedness of organisms through their DNA and proteins.
• Biogeography studies the distribution of species and how they have evolved in different environments.

Fossil Records

• Fossils are the preserved remains or traces of ancient organisms.
• They provide a chronological record of life's history.
• Fossils can show the intermediate forms of organisms, illustrating evolutionary transitions.

Comparative Anatomy

• Homologous structures are anatomical features that have a common evolutionary origin, even if they have different functions.
• Analogous structures are features that have similar functions but evolved independently.
• Vestigial structures are remnants of organs or structures that had a function in an ancestor but no longer do.

Molecular Biology

• DNA and protein sequences can be compared to determine the relatedness of different species.
• Closely related species have more similar DNA sequences.
• Conserved genes are genes that have remained relatively unchanged throughout evolutionary history, indicating their importance.

Biogeography

• The distribution of species around the world reflects their evolutionary history and the movement of continents.
• Endemic species are found only in a specific geographic area.
• Islands often have unique species that have evolved in isolation.

Speciation

• Speciation is the process by which new species arise.
• Allopatric speciation occurs when populations are separated by a physical barrier.
• Sympatric speciation occurs when new species arise within the same geographic area.

Allopatric Speciation

• A population is divided by a geographic barrier, such as a mountain range or body of water.
• The separated populations evolve independently due to different environmental conditions and genetic drift.
• Over time, the populations become so different that they can no longer interbreed.

Sympatric Speciation

• New species can arise within the same geographic area through mechanisms such as polyploidy, habitat differentiation, or sexual selection.
• Polyploidy is the duplication of chromosomes, which can lead to reproductive isolation.
• Habitat differentiation occurs when subpopulations within the same area use different resources.
• Sexual selection can drive the evolution of different mating behaviors or preferences.

Phylogenetic Trees

• Phylogenetic trees are diagrams that show the evolutionary relationships among organisms.
• They are based on shared characteristics, such as anatomical features or DNA sequences.
• Each branch point on the tree represents a common ancestor.

Evolutionary History

• The history of life on Earth has been marked by major evolutionary events, such as the origin of life, the evolution of photosynthesis, and the Cambrian explosion.
• Mass extinction events have also played a role in shaping the diversity of life.

Origin of Life

• Life is thought to have originated from non-living matter through a process called abiogenesis.
• The early Earth had different atmospheric conditions.
• Key steps in the origin of life may have included the formation of organic molecules, the assembly of polymers, and the formation of protocells.

Photosynthesis

• The evolution of photosynthesis allowed organisms to harness energy from the sun.
• This led to an increase in the amount of oxygen in the atmosphere.
• Oxygen-rich atmosphere supported the evolution of more complex life forms

Cambrian Explosion

• The Cambrian explosion was a period of rapid diversification of life.
• Many new types of animals appeared in a relatively short amount of time.
• This event may have been triggered by changes in environmental conditions or the evolution of new developmental genes.

Mass Extinctions

• Mass extinctions are events in which a large percentage of species on Earth go extinct in a relatively short amount of time.
• They can be caused by factors such as asteroid impacts, volcanic eruptions, or climate change.
• Mass extinctions can create new opportunities for the surviving species, leading to adaptive radiation.

Adaptive Radiation

• Adaptive radiation is the rapid diversification of a lineage into many different forms.
• It often occurs after a mass extinction event.
• The surviving species can evolve to fill the ecological niches left vacant by the extinct species.

Evolution and Human Health

• Understanding evolution is important for addressing many human health issues, such as antibiotic resistance, the evolution of viruses, and the development of new drugs.
• Antibiotic resistance evolves when bacteria are exposed to antibiotics, those that are resistant survive and reproduce, leading to a population of resistant bacteria.
• Viruses can evolve rapidly, making it difficult to develop effective vaccines and treatments.
• The study of evolution can provide insights into the development of new drugs that target specific molecules or pathways in disease-causing organisms.