Scientific Method: Attributes and Inquiry

Distinguishing Attributes of Science

• Scientific claims rely on empirical evidence, observations, and experimentation.
• Beliefs are rooted in personal or cultural convictions and lack testability.
• Scientific knowledge is generated through observation, hypothesis formation, experimentation, data analysis, and peer review.
• Science is limited to addressing natural phenomena and cannot address moral or aesthetic questions.

Principles of Scientific Inquiry

• A hypothesis is a testable explanation, while a prediction is the expected outcome if the hypothesis holds true.
• A scientific theory is a broad, well-supported explanation whereas a fact is a repeatedly confirmed observation.
• Experimental design includes independent and dependent variables, a control group, replication, and considering sample size.
• An experiment involves manipulating variables, while an observational study involves observation without intervention.

The Scientific Process

• The scientific process starts with observation and questions such as "Why do leaves change color in fall?"
• A hypothesis is formed, like "Temperature changes affect leaf color," leading to a prediction such as "Colder temperatures will cause earlier color change."
• Experiments should include controls, replication, and variable manipulation.
• Data collected can be quantitative (numbers) or qualitative (descriptions).

Evaluating Scientific Studies

• Credibility relies on peer-reviewed sources, reproducibility of results, and transparency in methodology.

Historical Perspectives of Evolution

• Plato believed in typological thinking, that species are fixed and perfect.
• Aristotle described a linear hierarchy of life forms.
• Darwin and Wallace proposed population thinking, that variation drives evolution.

Lamarck’s Hypothesis

• Lamarck hypothesized the inheritance of acquired traits, like giraffes stretching their necks.
• Acquired traits are not passed down genetically.

Darwin’s Influences

• Darwin's observations on the HMS Beagle showed variation among species like the Galápagos finches.
• Lyell's geology influenced the idea of slow evolutionary change.
• Malthus' essay highlighted population limits and competition for resources.

Darwin’s Tree of Life

• The tree of life represents common ancestry, showing how species diverge from shared ancestors.

Natural Selection

• Natural selection postulates that variation exists, traits are heritable for differential survival and reproduction.

Artificial vs. Natural Selection

• Artificial selection is human-directed breeding, like dog breeds.
• Natural selection is environment-driven trait selection, like camouflaged insects.

Evidence for Evolution

• The fossil record provides transitional forms.
• Biogeography studies geographic species distribution.
• Comparative anatomy shows homologous and analogous structures.

Evolution vs. Theory of Evolution

• Evolution is the change in allele frequencies over time.
• The Theory of Evolution explains the mechanisms behind evolution.

Gene Pool Concept

• The gene pool is the total genetic variation in a population.

Mutation

• Mutation is a source of genetic variation.
• Mutations impact on fitness can be beneficial, neutral, or harmful.

Genetic Drift

• Genetic drift involves random allele frequency changes, affected by sampling error.
• The founder effect is a new population from few individuals.
• The bottleneck effect is a population reduction that leads to reduced genetic variation.

Gene Flow

• Gene flow is the movement of alleles between populations, increasing genetic similarity.

Hardy–Weinberg Principle

• The Hardy-Weinberg principle states there is no evolution if allele frequencies remain constant.

Conceptual Framework

• Ecological and sexual selection are forms of natural selection.

Adaptation

• Adaptation refers to inherited beneficial traits and the process of acquiring adaptations.

Evolution by Natural Selection

• Peppered moths changing color due to pollution demonstrate evolution by natural selection.

Modes of Selection

• Directional selection shifts trait distribution.
• Stabilizing selection reduces variation.
• Disruptive selection favors extremes.

Balancing Selection

• Heterozygote advantage is exemplified by the sickle-cell trait.
• Frequency-dependent selection involves predators favoring common prey.

Speciation Process

• Speciation involves genetic isolation and divergence.

Reproductive Isolation

• Prezygotic isolation involves temporal and behavioral barriers.
• Postzygotic isolation produces sterile offspring.

Allopatric vs. Sympatric Speciation

• Allopatric speciation involves geographic separation.
• Sympatric speciation occurs in the same location, with different niches.

Major Developments in Evolution

• Photosynthesis and endosymbiosis drive biodiversity.

Mass Extinctions

• Mass extinctions impact diversity and open ecological niches.

Phylogenetic Trees

• Clades are groups with common ancestors.

Microbiomes

• Human health is affected by gut bacteria.

Land Adaptations in Plants

• Structural adaptations include roots and cuticles.
• Reproductive adaptations include seeds and pollen.

Key Features of Fungi

• Fungi feed through decomposition.

Defining Animals

• Animals are multicellular and heterotrophic.

Mollusk Classes

• Gastropods are snails.
• Cephalopods are octopuses.
• Bivalves are clams.

Vertebrate Innovations

• Jaws, limbs, and amniotic eggs are evolutionary milestones.