Biology Playlist Recap Flashcards

Characteristics of Life

  • Life is difficult to define, with many exceptions when considering its characteristics.
  • The video encourages viewers to think about characteristics of life and what differentiates living from non-living things.

Biological Levels of Organization

  • The biological levels of organization start with the cell, the smallest living unit (part of cell theory).
  • Cell theory:
    • The cell is the smallest living unit in all organisms.
    • All living organisms are made up of cells.
    • All cells come from pre-existing cells.
  • Cells combine to form tissues, tissues form organs, organs form organ systems, and organ systems form an organism.
  • An individual organism can be part of a population (same species), a community (different species), an ecosystem (including abiotic factors like rocks and temperature), a biome, and finally the biosphere.

Biomolecules

  • Four major macromolecules (biomolecules) are essential for living organisms:
    • Carbohydrates
    • Lipids
    • Proteins
    • Nucleic acids
  • Their building blocks (monomers) are:
    • Monosaccharides (carbohydrates)
    • Fatty acid and glycerol (lipids)
    • Amino acids (proteins)
    • Nucleotides (nucleic acids)
  • Monomers are true monomers for carbs, proteins, and nucleic acids.
  • Functions of biomolecules are vital for life.
  • A popular mnemonic helps remember the major elements in these structures.

Enzymes

  • Most enzymes are made of proteins.
  • Enzymes have an active site where a substrate binds.
  • Enzymes speed up reactions by breaking down or building up substrates.
  • Products are formed as a result of enzyme activity.
  • Digestive enzymes are specific for breaking down fats, sugars, or proteins.
  • Enzymes require a specific temperature and pH range to function correctly; if these conditions are not met, they can denature.

Cells: Prokaryotic vs. Eukaryotic

  • Prokaryotic cells lack a nucleus and other membrane-bound organelles.
  • Eukaryotic cells have a nucleus and other membrane-bound organelles.
  • Mnemonic: pro rhymes with no (no nucleus), and u rhymes with do (do have a nucleus).
  • Prokaryotes include bacteria and archaea, while eukaryotes include plants, animals, protists, and fungi.
  • Both prokaryotic and eukaryotic cells have common features like DNA, cytoplasm, ribosomes, and a cell membrane.
  • Eukaryotes exclusively contain membrane bound organelles like the nucleus, endoplasmic reticulum, Golgi apparatus, and mitochondria.

Cell Membrane (Plasma Membrane)

  • The cell membrane is essential for homeostasis as it controls what enters and exits the cell.
  • It is composed of phospholipids with polar heads and nonpolar tails.
  • Passive transport: Molecules move across the membrane without added energy, following the concentration gradient.
    • Simple diffusion
    • Facilitated diffusion (through a protein)
  • Active transport: Uses ATP to move molecules against the concentration gradient.
  • Water moves across the membrane through osmosis, either directly or via aquaporins.
  • Osmosis can be viewed as water moving from high to low water concentration or from low to high solute concentration.
  • Hypertonic areas have high solute concentration, and water moves towards them.

Organelles: Mitochondria and Chloroplast

  • In eukaryotes, mitochondria are involved in cellular respiration, while chloroplasts are involved in photosynthesis.
  • Cellular respiration breaks down glucose to produce ATP, which all organisms must make.
  • If oxygen is unavailable, some organisms use anaerobic respiration or fermentation.
  • Photosynthesis produces glucose using sunlight energy and occurs in chloroplasts in eukaryotic cells.
  • Reactants and products are switched between the two processes, but they are not simply the reverse of each other and have different steps.

Nucleus and DNA

  • The nucleus of a eukaryotic cell contains DNA.
  • DNA, a nucleic acid, carries genetic information found in almost all body cells.
  • A nucleotide, the monomer of DNA, consists of a phosphate, deoxyribose, and a nitrogenous base.
  • The sequence of bases determines genetic information.
  • Mnemonic: "Apples in the tree, cars in the garage" (Adenine pairs with Thymine, Cytosine pairs with Guanine).
  • DNA is tightly coiled into chromosomes; humans have 46 chromosomes (23 from each parent).
  • DNA consists of two antiparallel strands running five' to three' and three' to five'.

DNA Replication

  • DNA replication is necessary for creating new body cells for growth and repair.
  • Key player enzymes:
    • Helicase: unwinds DNA
    • Primase: lays down primers
    • DNA polymerase: builds a new strand in the five' to three' direction, requiring primers.
    • Ligase: seals Okazaki fragments on the lagging strand.
  • Due to the directional building, one strand is a lagging strand with Okazaki fragments.

Cell Cycle

  • The cell cycle includes:
    • G1 (cell growth)
    • S phase (DNA synthesis/replication)
    • G2 (further growth and preparation for division)
    • M phase (mitosis and cytokinesis)
  • G1, S, and G2 are part of interphase (non-dividing phase).
  • Checkpoints control whether a cell can continue through the cycle; if requirements aren't met, the cell undergoes apoptosis (self-destruction).
  • The cell cycle is controlled by proteins like CDK, cyclin, and p53.
  • Cancer cells bypass checkpoints and divide uncontrollably.

Mitosis

  • Mitosis is a type of cell division that produces identical body cells for growth and repair.
  • Chromosomes (condensed DNA and protein) are easily moved into new daughter cells.
  • Mnemonic: PMAT - prophase, metaphase, anaphase, and telophase.
  • Cytokinesis splits the cytoplasm, fully dividing the cell.

Meiosis

  • Meiosis produces gametes (sperm and egg cells) for sexual reproduction.
  • Gametes have half the number of chromosomes as body cells (haploid).
  • Body cells are diploid (two sets of chromosomes), while gametes are haploid (one set of chromosomes).
  • PMAT occurs twice in meiosis (Meiosis I and Meiosis II), resulting in four haploid cells.
  • These cells are genetically different due to independent assortment and crossing over.
  • Crossing over occurs during prophase I, where homologous chromosomes exchange information.

Genetics

  • In humans, sperm and egg cells have 23 chromosomes each; when combined, the fertilized egg has 46 chromosomes.
  • Genes, located on chromosomes, code for specific traits.
  • Genes come in different forms called alleles.
  • Example: PTC tasting gene has alleles for tasting (T, dominant) and non-tasting (t, recessive).
  • Genotypes and Phenotypes:
    • TT (homozygous dominant): PTC tasting
    • Tt (heterozygous): PTC tasting
    • tt (homozygous recessive): non-PTC tasting
  • Mendelian inheritance involves the expression of recessive alleles when a dominant allele is not present.

Types of Genetics

  • Mendelian genetics include monohybrid and dihybrid crosses, solved using Punnett squares.
  • Non-Mendelian inheritance includes:
    • Sex-linked traits
    • Multiple alleles
    • Incomplete dominance
    • Codominance
  • Incomplete Dominance vs. Codominance: In codominance, both alleles are expressed; in incomplete dominance, the phenotype is a blend of the two traits.

Pedigrees

  • Pedigrees track traits of interest (sex-linked or autosomal).
  • Females are represented by circles, males by squares; shaded shapes indicate individuals with the trait.

Protein Synthesis

  • DNA codes for proteins, which are involved in many traits and functions.
  • Two major steps in protein synthesis:
    • Transcription: mRNA is made in the nucleus.
    • Translation: occurs in the ribosome and produces a polypeptide chain of amino acids.
  • Other forms of RNA (rRNA, tRNA) are also involved.
  • Codon charts are used to determine which amino acids are produced.
  • Proteins often require folding to become functional.

Codons and Mutations

  • Codons are three-base sequences on mRNA that specify an amino acid.
  • tRNA has an anticodon complementary to the mRNA codon and carries the corresponding amino acid.
  • Gene Mutations:
    • Substitution
    • Deletion
    • Insertion
  • Insertions and deletions are more likely to cause frameshift mutations.
  • Frameshift mutations alter the reading frame, affecting multiple codons.
  • Chromosomal Mutations:
    • Duplication
    • Deletion
    • Inversion
    • Translocation
  • Mutations can be neutral, harmful, or beneficial, but they are random.

Natural Selection

  • Natural selection acts on populations where variety exists within a species due to meiosis or mutations.
  • Organisms with traits that provide a better fit for their environment (higher fitness) are more likely to survive and reproduce.
  • Fitness is determined by reproductive success (number of offspring).
  • Over time, the frequency of advantageous traits increases in the population.

Genetic Drift

  • Both genetic drift and natural selection are mechanisms of evolution.
  • In genetic drift, survival and reproduction are due to random chance, not necessarily biological fitness.
  • Examples of genetic drift include the bottleneck effect and founder effect.

Bacteria

  • Bacteria are unicellular prokaryotes.
  • Some bacteria are autotrophs (make their own food), and others are heterotrophs (consume organic material).
  • Bacteria lack a nucleus and membrane-bound organelles but have genetic material, cytoplasm, and ribosomes.
  • Bacteria can be helpful or harmful.
  • Helpful roles include breaking down food, acting as decomposers, making foods, and fixing nitrogen.
  • Harmful bacteria (pathogens) can be treated with antibiotics.

Viruses

  • Viruses are not considered living organisms because they are not cells and require a host to reproduce.
  • Viruses have genetic material (DNA or RNA) and a protein coat (capsid); some have envelopes.
  • Viruses reproduce using the lytic or lysogenic cycle.
  • Viral diseases (e.g., common cold, HIV, influenza) do not respond to antibiotics.

Classification of Living Organisms

  • Life is organized into three domains: Bacteria, Archaea, and Eukarya.
  • Taxonomy levels after domain are: kingdom, phylum, class, order, family, genus, and species.
    • Mnemonic: (i.e., "Dear King Philip Came Over For Good Spaghetti")
  • Scientific names (binomial nomenclature) are more reliable than common names.

Plants

  • Plants are autotrophs that provide a significant amount of Earth's oxygen.
  • Structure:
    • Nonvascular plants get water by osmosis.
    • Vascular plants have xylem (water transport) and phloem (sugar transport).
    • Chloroplasts capture light energy.
    • Stomata (pores) facilitate gas exchange, controlled by guard cells.
  • Reproduction:
    • Asexual reproduction
    • Sexual reproduction (primarily in flowering plants/angiosperms).
  • Angiosperm structures: petals, sepals, anther, filament, stigma, style, ovary.
  • Pollination & Fertilization: pollen transfer to stigma, pollen tube formation, sperm fertilizes egg and polar nuclei (double fertilization), ovules become seeds, ovary becomes fruit.

Ecology

  • Plants are producers in food chains/webs; consumers (heterotrophs) eat other organisms.

  • Food chains illustrate energy flow:

    • producers -> primary consumers -> secondary consumers -> tertiary consumers

  • Energy pyramid shows energy transfer between trophic levels (approximately 10% energy transfer).

  • Example Energy flow pyramid with 10,000 kcal at the base:

    • Trophic<br/>ewlinelevel<br/>ewline1:10,000<br/>ewlinekcalTrophic <br /> ewline level <br /> ewline 1: 10,000 <br /> ewline kcal
    • Trophic<br/>ewlinelevel<br/>ewline2:1,000<br/>ewlinekcalTrophic <br /> ewline level <br /> ewline 2: 1,000 <br /> ewline kcal
    • Trophic<br/>ewlinelevel<br/>ewline3:100<br/>ewlinekcalTrophic <br /> ewline level <br /> ewline 3: 100 <br /> ewline kcal
    • Trophic<br/>ewlinelevel<br/>ewline4:10<br/>ewlinekcalTrophic <br /> ewline level <br /> ewline 4: 10 <br /> ewline kcal

  • Energy is lost as heat or undigested material.

  • Food webs are complex networks of interacting food chains.

  • Biodiversity contributes to the sustainability of a community.

Ecological Succession

  • Ecological succession is the gradual change in an ecological community over time.
  • Primary succession: Occurs in new areas without soil like cooled lava flows.
    • Pioneer species (lichen, moss) colonize first, breaking down rock and forming soil.
    • Small vascular plants, shrubs, and trees follow.
  • Secondary succession: Occurs in areas with existing soil after an ecological disturbance (e.g., forest fire).
    • Small plants can quickly colonize the area.

Nutrient Cycles

  • Carbon cycle: Carbon is found in biomolecules, the ocean, rocks, fossil fuels, living organisms, and the atmosphere (as carbon dioxide).
    • Photosynthetic organisms take in carbon dioxide.
    • Cellular respiration releases carbon dioxide.
    • Decomposition releases carbon stored in sediments.
    • Burning fossil fuels releases carbon dioxide.
  • Nitrogen cycle: Nitrogen is important in building proteins and nucleic acids.
    • Nitrogen-fixing bacteria convert nitrogen into ammonia and ammonium.
    • Nitrifying bacteria convert ammonium to nitrates and nitrites.
    • Plants assimilate nitrates and nitrites.
    • Decomposers return ammonia and ammonium to the soil (ammonification).
    • Denitrifying bacteria convert nitrates and nitrites back into nitrogen gas.

Ecological Relationships

  • Predation: One organism (predator) eats another (prey).
  • Competition: Organisms compete for resources.
  • Symbiotic Relationships:
    • Commensalism: One organism benefits, the other is neutral.
    • Parasitism: One organism benefits (parasite), the other is harmed (host).
    • Mutualism: Both organisms benefit.

Human Body Systems

  • 11 Body Systems:
    • Circulatory
    • Digestive
    • Endocrine
    • Excretory
    • Immune/Lymphatic
    • Integumentary
    • Muscular
    • Nervous
    • Reproductive
    • Respiratory
    • Skeletal
  • Systems don't work in isolation but work together.