Key Concepts in Biology: Units 1-6 Overview

Six Characteristics of Living Things

Made of cells, obtain and use energy, grow and develop, reproduce, respond to stimuli, maintain homeostasis.

Hypothesis

A testable prediction.

Conclusion

A summary of the results from an experiment.

Theory

A well-supported and widely accepted explanation of natural phenomena.

Law

A statement based on repeated experimental observations that describes a phenomenon.

Create and Interpret Graphs

Be able to read line, bar, and pie graphs; identify trends, independent/dependent variables, and data relationships.

Levels of Biological Organization

Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ system → Organism.

Essential Chemistry of Water

Water is polar, cohesive, adhesive, and a universal solvent; it has high heat capacity and participates in hydrogen bonding.

pH Scale

Ranges from 0-14; below 7 = acidic; 7 = neutral; above 7 = basic (alkaline).

Prokaryotic Cells

No nucleus, smaller, simpler (e.g., bacteria).

Eukaryotic Cells

Have a nucleus, organelles, and are more complex (e.g., animals, plants).

1st Law of Thermodynamics

Energy cannot be created or destroyed.

2nd Law of Thermodynamics

Energy transformations increase entropy; some energy is lost as heat.

Photosynthesis

CO₂ + H₂O + sunlight → C₆H₁₂O₆ + O₂.

Cellular Respiration

C₆H₁₂O₆ + O₂ → CO₂ + H₂O + ATP.

Anabolism

Building complex molecules (requires energy).

Catabolism

Breaking down molecules (releases energy).

Mitosis

2 identical diploid cells; for growth/repair.

Meiosis

4 unique haploid cells; for reproduction.

Dominant Alleles

Expressed if present.

Recessive Alleles

Expressed only if two copies are present.

Codominance

Both alleles are fully expressed (e.g., AB blood type).

Incomplete Dominance

Blend of traits.

Polygenic Traits

Multiple genes influence a trait (e.g., skin color).

Protein Synthesis Steps

Transcription: DNA → mRNA (in nucleus); Translation: mRNA → Protein (in ribosome; tRNA brings amino acids).

DNA

Double-stranded, deoxyribose, bases A-T-C-G.

RNA

Single-stranded, ribose, bases A-U-C-G.

DNA Replication

Semi-conservative; DNA unzips and each strand serves as a template.

Classification System

Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.

Mechanisms of Evolutionary Change

Natural selection, mutation, gene flow, genetic drift.

Speciation

Formation of new species due to reproductive isolation and genetic divergence.

Matter & Energy in Ecosystems

Energy flows (one-way), matter cycles (e.g., carbon, nitrogen).

Human Environmental Impact

Pollution, habitat loss, climate change; affects biodiversity and biogeochemical cycles (e.g., carbon/nitrogen cycles).