Biology MCAS Super Notes

Ecology

• Rule of 10: Only 10% of energy is passed from one trophic level to the next. Energy is lost as heat.
• Species compete for the same food sources, space, water, and energy.
• Source of all energy: The Sun, with the energy pyramid having the top level (top predators) with the least energy and the bottom (producers) with the most.
• Fungi: Heterotrophs serving as decomposers, breaking down dead organic matter and recycling nutrients back to the soil.

Species Interactions

Population Dynamics

• Population Growth:
  • Increases due to immigration and birth rates.
  • Decreases due to emigration and death rates.
• Population Growth Condition: Overall growth occurs when birth rate exceeds death rate under constant factors.

Carbon Cycle Processes

• Cycle: Photosynthesis and cellular respiration are interconnected; they use the products of one as reactants for the other.
• Carbon Storage: Carbon can be in the air, in soil, or living organisms, transitioning between these states.
• Carbon Combustion: Burning fuels releases CO_2, while fossilization stores carbon in the Earth.
• Climate Change: Caused by an increase in greenhouse gases (e.g., CO_2), leading to warmth due to trapped solar energy.

Human Impact

• Invasive Species: Thrive in new habitats without natural predators brought by human actions.
• Overharvesting: Humans consume resources faster than they can regenerate.
• Habitat Fragmentation: Human structures divide ecosystems, adversely affecting wildlife.
• Biodiversity: Higher biodiversity leads to more stable ecosystems.
• Conservation Efforts: Include captive breeding, ecotourism, and pollution mitigation.

Cellular Biology

• Eukaryotes vs. Prokaryotes:
  • Eukaryotes: Have a nucleus, complex organelles, often multicellular.
  • Prokaryotes: Lack a nucleus, simpler organelles, often single-celled.
• Phospholipid Structure: Composed of a hydrophilic head and hydrophobic tails.
• Membrane Proteins: Facilitate signaling and molecule transport.

Reproductive Strategies

• Sexual Reproduction:
  • Increases genetic diversity through crossover, random assortment, and fertilization.
• Asexual Reproduction (Binary Fission): Bacteria replicate by making identical copies.

Cell Cycle and Division

• Cell Cycle Phases: G1 → S → G2 → Mitosis (M phase). DNA replication occurs during S phase.
• Mitosis: Produces identical diploid somatic cells (2n) for growth and repair.
• Meiosis: Produces haploid gametes (n) for sexual reproduction, ensuring diversity.

Transport Mechanisms

• Osmosis: Movement of water across a membrane, driven by solute concentration.
  • Type of Solutions: Hypertonic (more particles), Hypotonic (fewer particles), Isotonic (equal concentration).

Chemistry of Life

• Essential Elements for Life: CHNOPS (Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorous, Sulfur).
• Energy Storage: Sugars (e.g., glucose) store energy, releasing it through bond breakage.
  • Sugars typically end in -ose; enzymes end in -ase.
• Enzymes: Proteins that perform biochemical reactions, with optimal conditions for temperature, pH, and concentration.

Macromolecules

Genetics

• DNA Structure: Double helix (nucleotides ATCG); RNA is single-stranded (AUCG).
• Replication and Transcription:
  • DNA Replication: DNA to DNA in the nucleus (A-T, C-G).
  • Transcription: DNA to RNA in the nucleus (A-U, C-G).
  • Translation: RNA to protein at ribosomes in the cytoplasm (codon-anticodon matching).
• Mutation: Changes in DNA sequence that may affect protein function (can lead to diseases like cancer).

Genetic Concepts

• Genotype: Genetic makeup of an organism.
• Phenotype: Observable traits influenced by genotype.
• Punnett Squares: Tools for predicting offspring traits based on parental genotypes (e.g., Sperm (23) + Egg (23) = Zygote (46) ).
• Homozygous vs. Heterozygous: Homozygous = same alleles; Heterozygous = different alleles.
• Laws of Inheritance:
  • Law of Segregation: Alleles segregate in pairs.
  • Law of Dominance: Dominant alleles mask recessive ones.
  • Law of Independent Assortment: Alleles are inherited independently.
• X-linked Traits: Inherited via X chromosome; females need two copies to express, while males need only one.
• Blood Type Genetics: A and B alleles are codominant, O is recessive.

Evolution

• Common Ancestry: All life forms are related through common ancestors; changes over time lead to evolution.
• Natural Selection:
  • Environmental factors influence which traits are advantageous for survival.
  • Example: Darwin's finches evolved different beak shapes based on food sources.
• Genetic Evidence: DNA, proteins, and amino acid sequences provide strong evidence of evolutionary relationships.
• Comparative Anatomy: Evidence from fossils, homologous structures, and vestigial organs underpin evolution reflection.
• Endosymbiosis Theory: Eukaryotic cells originated from symbiotic relationships with prokaryotes (e.g., mitochondria and chloroplasts).
• Viruses: Not considered living; they require hosts for reproduction and can evolve resistance to treatments.
• Sexual vs. Artificial Selection: Organisms may be selected based on desired traits either through natural or human-guided processes.
• Isolation Factors: Geographic and behavioral barriers may lead to speciation when populations diverge significantly.

Human Anatomy

• Respiratory System: Alveoli facilitate gas exchange (O2 in, CO2 out).
• Digestive System: Small intestine absorbs nutrients; large intestine removes water.
• Renal System: Kidneys filter blood and produce urine.
• Circulatory System: Heart pumps blood throughout the body.
• Musculoskeletal System: Muscles create movement; skeleton provides structure with ligaments and tendons for support.
• Nervous System: Processes signals, outputs responses; includes sensitivity and motor responses.
• Homeostasis: Regulation of internal conditions (e.g., blood sugar, body temperature).
  • Insulin lowers blood sugar; glucagon raises it.
  • Sweating cools the body; shivering warms it.
• Feedback Loops:
  • Positive feedback loops stimulate processes (e.g., childbirth).
  • Negative feedback loops regulate responses to maintain stability.
• Endocrine System: Releases hormones to coordinate physiological responses.