Hypothesis and Variables

Hypothesis

• Tentative explanation for an observation or scientific problem
• Testable through further investigation

Variable

• Something that can vary or change

Independent Variable

• Manipulated variable in an experiment
• Its presence or degree determines changes in the dependent variable

Dependent Variable

• Observed variable in an experiment
• Its changes are determined by the independent variable(s)

Control

• A standard for comparison in an experiment

Sources of Error in Experiments

• Instrumental error: Lack of calibration
• Personal error: Inaccurate observations
• Sampling error: Small or non-random sample size
• Replication error: Lack of consistency
• Experimental design flaws
• Measurement error: Lack of accuracy and precision

Basic Steps for an Experiment

• Plan the research, including ethical considerations
• Design the experiment, focusing on variable interaction
• Summarize observations using descriptive statistics
• Reach consensus about statistical inference
• Document and present the results

Types of Observations

• Qualitative: Described by words, subjective descriptions like color or smell, recorded using terms or photos
• Quantitative: Numerical values from counts or measurements, frequently require instruments

Replication of Experiments

• Demonstrates response variability
• Accounts for limited resource effects
• Shows differences between pairs of means
• Ensures reliability
• Maintains consistency in methods, procedures, and equipment
• Allows proper data analysis and interpretation
• Helps form scientifically literate viewpoints with valid data

Organic Molecules

• Contain carbon, found in living things

Carbohydrates

• Major energy source, includes sugars and starches
• Made of carbon, hydrogen, and oxygen (2:1 hydrogen:oxygen ratio)
• Used by plants and animals for cell structure

Proteins

• Nitrogen-containing chains of amino acids
• 20 amino acids form diverse proteins
• Can be enzymes, hormones, antibodies, or structural components

Lipids

• Water-insoluble fats and oils
• Composed of glycerol and fatty acids
• Provide insulation, store energy, cushion organs, found in membranes
• Saturated (single bonds) or unsaturated (double bonds)

Nucleic Acids

• Direct protein synthesis
• Carry genetic information
• Two types: DNA and RNA

Cell Organelles

• Chloroplast: Captures solar energy for photosynthesis (plants, algae)
• Golgi Body: Packages and distributes products
• Lysosomes: Digests excess products and food particles
• Mitochondria: Transforms energy through respiration
• Nucleus: Contains DNA, controls activities
• Ribosome: Produces proteins
• Vacuole: Stores substances
• Cell Membrane: Phospholipid bilayer, controls transport, maintains homeostasis
• Cell Wall: Rigid outer layer (plants, bacteria)
• Cytoplasm: Fluid containing organelles
• Endoplasmic Reticulum: Site of reactions
  • Rough ER: Contains ribosomes
  • Smooth ER: Lipid production
• Cytoskeleton: Provides structure
  • Microfilaments: Fibers
  • Microtubules: Cylinders

Cell Types

• Unicellular: Single, independent cell
• Multicellular: Specialized cell groups forming tissues, organs, and systems
• Prokaryote: Nuclear material without a membrane, no membrane-bound organelles (bacteria)
• Eukaryote: Defined nucleus with membrane, membrane-bound organelles (plants, animals, fungi, protists)

Cell Specialization

• Cells >> tissues >> organs >> organ systems >> organism
• Each cell performs a specific function
• Specialized cells may have unique organelles
• Cell design is dictated by function
• Multicellular organisms have greater specialization

Cell Theory

• The cell is the basic unit of life
• All organisms are composed of cells
• All cells come from pre-existing cells

Cell Transport

• Passive Transport: No energy needed, with concentration gradient
  • Diffusion: Movement from high to low concentration
  • Osmosis: Diffusion of water from high to low concentration
  • Facilitated Transport: Carrier molecule assists movement
• Active Transport: Requires energy, against concentration gradient
  • Endocytosis: Large particles enter the cell
  • Exocytosis: Large particles leave the cell

Homeostasis

• Internal equilibrium maintained by the plasma membrane regulating entry and exit of substances.
• Selectively permeable membrane
• Effect of Concentration:
  • Hypotonic: Water in, cell bursts
  • Hypertonic: Water out, cell shrinks
  • Isotonic: Equilibrium maintained
• Self-regulating mechanism that maintains internal conditions
• Cells communicate needs via chemical messengers
• Hypothalamus regulates homeostasis by sending signals to adjust the interstitial fluid
• Negative Feedback: Glucose/Insulin levels
• Positive Feedback: Blood platelets/clotting

Biochemical Reactions

• Chemical bonds formed and broken, impacting life functions
• Cellular Respiration: Food converted to energy
  • Glycolysis (anaerobic)
  • Citric Acid Cycle/Electron Transport Chain (aerobic)
  • C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (36 ATP)
• Photosynthesis: Plants convert sunlight to carbohydrates
  • 6CO2 + 6H2O + Energy → C6H12O6 + 6O2
• ATP: Stores and releases energy
  • ATP ↔ ADP + P + Energy
• Fermentation: Anaerobic ATP production
  • Lactic Acid Fermentation (muscle cells): Glucose → Lactic Acid + 2ATP
  • Alcoholic Fermentation (plant cells): Glucose → CO2 + Alcohol + 2ATP

Aerobic and Anaerobic Respiration

• Aerobic Respiration: Requires oxygen, releases energy from glucose, produces ATP
• Anaerobic Respiration: No oxygen needed, less energy produced, called fermentation, adaptation for oxygen-lacking environments

Comparison of Cellular Respiration, Photosynthesis, and Chemosynthesis

Enzymes

• Special proteins regulating biochemical reactions Function:
  • Provide energy, build cells, aid digestion
  • Break down complex molecules (substrate=reactant)
  • Catalysts (speed up reactions)
• Affected by pH, temperature, quantity

DNA & RNA

• Nucleic acids of nucleotides
• Nucleotides have phosphate, sugar, and nitrogenous base

Comparison of DNA and RNA

Protein Synthesis

• Transcription (mRNA from DNA) and Translation (mRNA to protein at ribosomes)

Asexual and Sexual Reproduction

• Asexual Reproduction: Single parent produces identical offspring (clones), common in unicellular, quick process.
  • Budding, binary fission, conjugation
• Sexual Reproduction: Fusion of haploid sex cells, genetic variation, common in multicellular, slow process
• Meiosis: Formation of gametes (sex cells)

Cell Division

• Process of copying and dividing a cell
• Unicellular organisms duplicate via asexual reproduction
• Multicellular organisms grow, develop, repair
• Three Types : Binary fission, Mitosis and Meiosis

Comparison of Mitosis and Meiosis

Genetics

• Study of heredity
• Gregor Mendel's pea plant experiments
  • Trait: Inherited characteristic
  • Gene: Instructions for traits (alleles)
  • Homozygous: Identical alleles (BB or bb)
  • Heterozygous: Different alleles (Bb)
  • Dominant: Controlling allele (capital letter)
  • Recessive: Hidden allele (lowercase letter)
  • Genotype: Genetic makeup (letters)
  • Phenotype: Physical appearance (description)
  • Monohybrid: One-trait cross
  • Dihybrid: Two-trait cross
  • Punnett Square: Probability of genetic cross results
  • Pedigree: Maps genetic traits across generations
  • Karyotype: Chart of chromosome pairs
  • Test Cross: Mating of unknown genotype with known genotype

Mendel's Laws of Heredity

• Law of Dominance: Dominant allele prevents recessive allele expression
• Law of Segregation: Gene pairs separate during gamete formation
• Law of Independent Assortment: Different gene pairs separate independently during gamete formation

Mutations

• Change in genetic code, passed to new cells or offspring
• Gene Mutation: Change in a single gene
• Chromosome Mutation: Change in many genes
• Spontaneous or caused environmental mutagens

Sex Chromosomes

• 23rd pair
  • Males: XY
  • Females: XX
• Sex-Linked Traits: Traits on sex chromosomes (X-linked from mother)

Other Patterns of Inheritance

• Linked Traits: Genes inherited together
• Multiple Alleles: More than two alleles for a trait
• Polygenic Inheritance: Many genes control one trait
• Codominance: Both homozygous phenotypes expressed in heterozygotes
• Incomplete Dominance: Heterozygote phenotype is intermediate
• Dominance/Recessiveness: Observed trait controlled by homozygous genotype

Sources of Variation

• Crossing Over: Gene exchange between chromosomes during meiosis
• Nondisjunction: Chromosome pairs don’t separate during meiosis
  • Trisomy (extra chromosome) or monosomy (one less chromosome)

Genetic Variation

• Influenced by crossing over, mutations, genetic engineering, random assortment, natural selection
• Controlled by sexual reproduction
• Gene expression is regulated by turning genes on/off or amount of action expression
• Environment can influence magnitude of gene expression

Laws of Probability and Punnett Squares

• Fertilization must occur at random
• Used to predict offspring genotypes and phenotypes
• Results are expected, not actual

Genetic Engineering (Genomics)

• Biotechnology
• Gene transfer from one organism to another
• Recombinant DNA produced
• Applications in medicine, environment, industry, agriculture
• Human Genome Project, DNA fingerprinting

Origins of Life

• Biogenesis: Living organisms from other living organisms
• Spontaneous Generation/Abiogenesis: Mistaken idea of life from nonliving materials
• Protocells: Membrane-enclosed structures with life activities

Natural Selection and Theory of Evolution

• Charles Darwin
• Survival and reproduction of best-suited organisms Adaptive changes:
  • Adaptation – organisms with the most suited traits will survive
  • Evolution – change in a species over time (not a single individual, but the group)

Microevolution vs. Macroevolution:

• Microevolution: Evolution within a species; results from genetic variation and natural selection within a population, involves antibiotic resistance
• Macroevolution: Evolution between species; convergent, divergent, adaptive radiation
• Speciation: Formation of new species, involves geographic and reproductive isolation

Classification

• Understanding organism relationships and differences
• Taxonomy: Branch of biology for grouping and naming organisms
• Historical Classification Systems
  • Aristotle: Plants and animals
• Carolus Linnaeus: Two kingdoms (plants, animals), genus and species, binomial nomenclature

Levels of Classification:

• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

Kingdoms

• Six kingdoms: Archaebacteria, Eubacteria, Protista, Fungi, Plantae, Animalia
• Basis of current classification: phylogeny, DNA/biochemistry, embryology, morphology

Comparison of Eukaryote to Prokaryote

• Prokaryote – has nuclear material in the center of the cell, but is not enclosed
• Eukaryote – contain a clearly defined nucleus enclosed by a nuclear membrane

Comparison of Kingdom Characteristics

Current classification systems reveal six kingdoms, split Monera into Archaebacteria and Eubacteria

Viruses

• Non-living, nucleic acid with protein coat
• Use living cells to replicate
• Lytic and lysogenic cycles
• Infect animals, plants, bacteria
• Do not respond to drugs
• Immunity required

Dichotomous Keys

• Identify organisms using contrasting characteristics

Types of Organisms

• Plants: Spore-producing and Seed-producing
• Invertebrates: No Backbone
• Vertebrates: Have backbone

Plants

• Spore-Producing Plants: nonvascular (mosses), vascular
• Seed Producing Vascular Plants: Gymnosperms (cone-bearing) and Angiosperms (Flowering)

Invertebrates

• No Backbone and types of symmetry
• Sponges (Porifera) - No symmetry
• Cnidarians (Coelenterata) - Radial Symmetry
• Flatworms (Platyhelminthes) - Bilateral symmetry
• Roundworms (Nematoda) - Radial Symmetry
• Segmented Worms - bilateral symmetry
• Mollusks (Mollusca) -Hard outer shell (calcium carbonate)
• Arthropods (Arthropoda) - Segmented Body, Pollinators, Bilateral symmetry
• Echinoderms (Echinodermata) - radial symmetry

Vertebrates

• Skeletal Endoskeleton, bilateral Symmetry
• Jawless Fishes
• Cartilaginous Fishes
• Bony Fishes
• Amphibians
• Reptiles
• Birds
• Mammals

Representative Groups and Essential Life Functions

• Unicellular Protists
• Annelid Worms
• Insects
• Amphibians
• Mammals
• Nonvascular Plants
• Angiosperms
• Gymnosperms

Major Systems and Organs:

• Reproduction – production of offspring
• Growth – increase in the amount of living material and formation of new structures
• Development – all the changes that take place during the life of an organism

Microorganisms:

• Living organisms, usually unicellular bacteria

Benefits:

• Help us to digest food
• Encourage normal development of the immune system
• Fight off bad organisms

Infectious diseases:

• Bacteria
• Viruses
• Fungi
• Parasites
• The Lymphatic System

Antibiotic Resistance:

• Some bacteria are resistant to antibiotics because they have enzymes that can destroy the antibiotics or because of genetic mutation that allow them to grow despite the antibiotics.
• Overuse of antibiotics has led to the development of resistant bacteria:

Animal Behavioral Adaptations

• Behavior – animal’s response to a stimulus
• Innate behavior – instinct; influenced by genes
  • Ex: bird defending its nest
• Learned behavior – changed by experience ex. training a pet to respond to a specific name
• Social behavior – interactions between members of same species
  • ex. mating and caring for offspring
• Territorial behavior – organisms defend an area to keep out other organisms ex. animal marking trees
• Reflex – automatic, neuromuscular action
  • ex. knee jerk
• Taxis – response to a directional stimulus; organism is motile First Line of Immune Defense:
• Physical Barriers - skin, mucous membranes (linings of the mouth, nose, eyelids), airways, stomach acid, pancreatic enzymes, bile, intestinal secretions, urinary secretions

Adaptive Responses

• Defenses against infection
• Blood
• Inflammation
• Fever Third Line of Immune Defense:
• Immune Response

•  Natural Immunity
  

•  Acquired Immunity
  

•  Immunization
  

• Active Immunization
• Passive Immunization
• External Defenses
• Antibiotics
• Hygiene

Circadian Rhythms and Rhythmic Behavior

• 24 hour cycle in plants, animals, fungi, and bacteria
• Biological rhythms can be daily, weekly, seasonal, annual
• Can be influenced by external factors such as sunlight and temperature
• Rhythmic behavior can be passed through genes to offspring
• Include behaviors such as sleeping, eating, brainwave activity, hormone production, cell regeneration, mating and sexual reproduction, hibernation, estivation, etc.

Structural Adaptations

• Mimicry – structural adaptation that allows one species to resemble another species; may provide protection from predators
• Camouflage – structural adaptation that enables species to blend with their surroundings; allows a species to avoid detection

Behavioral Adaptations

• Migration – instinctive seasonal movements of animals from place to place
• Emigration – movement of individuals from a population; leaving the population
• Immigration – movement of individuals into a population
• Hibernation – state of reduced metabolism occurring in animals that sleep during parts of cold winter months
  • ex. an animal’s temperature drops, oxygen consumption decreases, and breathing rate declines
• Estivation – state of reduced metabolism that occurs in animals living in conditions of intense heat Mating / Reproduction – production of offspring for the survival of the species; can be seasonally scheduled

Plant Tropism

• Growth responses that result in curvature of plant organs towards or away from stimuli due to different rates of elongation
• Geotropism – roots have positive geotropism/stems have negative geotropism
• Phototropism – leaves response to light
• Hydrotropism – roots response to water
• Thigmotropism – venus flytrap response to touch
• Chemotropism – plants response to chemicals

Energy Flow in an Ecosystem

• Sunlight as the main energy source
• Energy flow: sun > producers > consumers.

Structure of an Ecosystem

• Organism > Species > Population > Community > Ecosystem > Environment
• Species – group of organisms that can interbreed
• Population – units of single species
• Community – groups of interacting populations
• Ecosystem – groups of interacting communities
• Habitat – place where an organism lives
• Niche – organism’s role within its habitat

Groups of Organisms

Symbiotic Relationships

Symbiosis – permanent, close association between one or more organisms of different species

• Mutualism – both species benefit : ex. in subtropical regions, ants protect acacia trees by fighting invaders, acacia tree provides nectar to ants
• Commensalism – symbiotic relationship in which one species benefits and the other species is neither harmed nor benefited ex. Spanish moss grows on and hangs from limbs of trees, but does not obtain any nutrients from tree, nor harm the tree Parasitism – symbiotic relationship in which one organism benefits at the expense of another, usually another species : ex. parasites such as bacteria, roundworms, tapeworms live in the intestines of organisms to obtain nutrients and reproduce, but cause disease in the organisms

Food Chain

• Path of energy from producer to consumer
• Each level is called a trophic level (trophic = energy)
• Approximately 10% energy is transferred to next level
• 90% used for personal metabolism and development

Food Web

• Interconnected food chains
• Shows all possible feeding relationships at each trophic level in a community

Ecological Pyramid

• Representation of energy transfer
• Pyramid of Energy – each level represents energy available at that level, 90% decline
• Pyramid of Biomass – each level represents amount level above needs to consume Pyramid of Numbers – each level represents number of organisms consumed by level above it

Survival Factors

• Natural Selection, Adaptation (Behavioral or Physiological), Limiting Factors (Environmental), Genetic Mutations
• Biodiversity, Evolution (Macroevolution vs. Microevolution)

Characteristics of Living Things:

• require food for energy to carry out life processes
• use energy to maintain homeostasis
• respond to stimuli in the environment
• grow and develop
• reproduce similar offspring
• pass genetic information to their offspring
• composed of cells
• composed of organic based compounds

Cycles:

• type of life cycle found in some algae, fungi, and all plants where an organism alternates between a haploid (n) gametophyte generation and a diploid (2n) sporophyte generation

(Matter cannot be created nor destroyed, but can be converted/recycled to other forms)

• Water Cycle – water is recycled through evaporation, condensation, precipitation, runoff, groundwater, aquifers, respiration, transpiration, excretion, decomposition
• Nitrogen Cycle – producers take in nitrogen compounds in soil and pass to consumers that consume the producers; decomposers (bacteria) break down nitrogen compounds and release nitrogen gas to air or usable nitrogen so the soil
• Carbon Cycle – carbon is recycled through respiration, photosynthesis, fuel combustion, decomposition; carbon can be atmospheric or dissolved, or can be found in organic compounds within the body

Ecology Field Study:

• specific methods and procedures to study habitat

Ecological Succession

• orderly, natural changes, and species replacements
• Primary Succession – soil development
• Secondary Succession – soil already present

Types of Ecosystems (Biomes)

Aquatic

• based on flow, depth, temperature, chemistry

Terrestrial

• based on geography, rainfall, temperature

Human Impact

• cause Extinction of species
• growing demand on Enviornment