Evolution
Change in a kind of organism over time; process by which modern organisms have descended from ancient organisms.
Theory
well-tested explanation that unifies a broad range of observations
Fitness
Ability of an organism to survive and reproduce in its environment
fossil record
the millions of fossils that scientists have collected
homologous structures
similar structures that related species have inherited from a common ancestor
analogous structures
similarities among unrelated species that result from convergent evolution
vestigial structures
remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species.
Embryology
study of embryos and their development
genetic drift
A change in the allele frequency of a population as a result of chance events rather than natural selection.
Mutation
change in a DNA sequence that affects genetic information
founder effect
change in allele frequencies as a result of the migration of a small subgroup of a population
bottleneck effect
A change in allele frequency following a dramatic reduction in the size of a population
Biological Resistance
The natural or genetic ability of an organism to avoid or repel attack by biotic agents
gene pool
Combined genetic information of all the members of a particular population
Natural Selection
A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.
Adaptation
inherited characteristic that increases an organism's chance of survival
Artificial Selection
Selection by humans for breeding of useful traits from the natural variation among different organisms
Convergent Evolution
Process by which unrelated organisms independently evolve similarities when adapting to similar environments
Divergent Evolution
when two or more species sharing a common ancestor become more different over time
Coevolution
Process by which two species evolve in response to changes in each other
Adaptive Radiation
An evolutionary pattern in which many species evolve from a single ancestral species
Punctuated Equilibrium
Pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change
Gradualism
The theory that evolution occurs slowly but steadily
Reproductive Isolation
Separation of species or populations so that they cannot interbreed and produce fertile offspring
Behavioral Isolation
Form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding
Geographical Isolation
form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water
Temporal Isolation
form of reproductive isolation in which two populations reproduce at different times
Law of Segregation
Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete
law of independent assortment
Mendel's second law, stating that allele pairs separate from one another during gamete formation
Law of Dominance
Law that states that some alleles are dominant and some are recessive
Genotype
genetic makeup of an organism
Phenotype
An organism's physical appearance, or visible traits.
Allele
Different forms of a gene
Homozygous
Having two identical alleles for a particular gene
Heterozygous
having two different alleles for a trait
Trait
A characteristic that an organism can pass on to its offspring through its genes.
Hybrid
An organism that has two different alleles for a trait
Punnett Square
A chart that shows all the possible combinations of alleles that can result from a genetic cross
Gene
A segment of DNA on a chromosome that codes for a specific trait
Dominant
An allele that is always expressed
Recessive
An allele that is masked when a dominant allele is present
Purebred
An organism that always produces offspring with the same form of a trait as the parent.
true-breeding
term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate
monohybrid cross
A cross between two individuals, concentrating on only one definable trait
Law of Segregation
Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete
law of independent assortment
Mendel's second law, stating that allele pairs separate from one another during gamete formation
Law of Dominance
Law that states that some alleles are dominant and some are recessive
Genotype
genetic makeup of an organism
Phenotype
An organism's physical appearance, or visible traits.
Allele
Different forms of a gene
Homozygous
Having two identical alleles for a particular gene
Heterozygous
having two different alleles for a trait
Trait
A characteristic that an organism can pass on to its offspring through its genes.
Hybrid
An organism that has two different alleles for a trait
Punnett Square
A chart that shows all the possible combinations of alleles that can result from a genetic cross
Gene
A segment of DNA on a chromosome that codes for a specific trait
Dominant
An allele that is always expressed
Recessive
An allele that is masked when a dominant allele is present
Purebred
An organism that always produces offspring with the same form of a trait as the parent.
true-breeding
term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate
monohybrid cross
A cross between two individuals, concentrating on only one definable trait
Cloning
Making a genetically identical copy of DNA or of an organism.
DNA fingerprinting
analysis of fragments of DNA as a form of identification; can be used for paternity tests or crime scenes
Recombinant DNA
DNA that has been formed artificially by combining DNA from different organisms.
polymerase chain reaction (PCR)
technique that allows molecular biologists to make many copies of a particular gene
genetically modified organism (GMO)
an organism produced by copying genes from a species with a desirable trait and inserting them into another species
CRISPR
A specific type of gene therapy that can cut out or replace genes.
genetic engineering
A technology that includes the process of manipulating or altering the genetic material of a cell resulting in desirable functions or outcomes that would not occur naturally.
mutation
change in a DNA sequence that affects genetic information
point mutation
Gene mutation involving changes in one or a few nucleotides.
substitution mutation
point mutation in which one nitrogeneous base (nucleotide) is changed to another
frame-shift mutation
mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide
deletion mutation
a mutation in which one or more pairs of nucleotides are removed from a gene
insertion mutation
the addition of one or more nucleotide base pairs into a DNA sequence
Mutagen
A chemical or physical agent that interacts with DNA and causes a mutation.
Ecology
the scientific study of interactions among organisms and between organisms and their environment
Mitosis
cell division in which the nucleus divides into nuclei containing the same number of chromosomes.
Chlorophyll
Green pigment in plants that absorbs light energy used to carry out photosynthesis.
Primary Succession
type of succession that occurs in an environment that never had soil (after lava flow, retreating glacier, etc)
Asexual Reproduction
A reproductive process that involves only one parent and produces offspring that are identical to the parent.
Chloroplast
An organelle found in plant and algae cells where photosynthesis occurs.
Producer
also known as an autotroph; makes its own energy using photosynthesis or chemosynthesis
Meiosis
a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes.
Pigment
Light-absorbing molecule.
Biosphere
the parts of the planet including land, water or atmosphere in which all life exists
Sexual Reproduction
A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents.
Light Independent Reactions (Calvin Cycle)
set of reactions in photosynthesis that do not require light; energy from ATP and NADPH is used to build high-energy compounds such as sugar; also called the Calvin cycle.
Secondary Succession
type of ecological succession where soil and vegetation were present; usually occurs after a disturbance (old farmland, natural disasters, etc)
Binary Fission
A form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size
Light Dependent Reactions
reactions of photosynthesis that use energy from light to produce ATP and NADPH.
Photosynthesis
process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches.
Gametes
sex cells
Consumer
also known as a hetertroph; eats other organisms for food; uses cellular respiration
Population
group of individuals that belong to the same species and live in the same area
Somatic Cells
Any cells in the body other than reproductive cells
Autotroph
An organism that makes its own food (producer)
Exponential growth
a type of growth whose rate becomes more and more rapid because there are no/few limiting factors
Haploid
An organism or cell having only one complete set of chromosomes.
Heterotroph
organism that obtains energy from the foods it consumes; also called a consumer.
ATP
(adenosine triphosphate) main energy source that cells use for most of their work.
Diploid
containing two complete sets of chromosomes, one from each parent.
Food chain
a hierarchical series of organisms each dependent on the next as a source of food
Food web
a system of interlocking and interdependent food chains
Cytokinesis
Division of the cytoplasm during cell division
Thylakoid
A flattened membrane sac inside the chloroplast, used to convert light energy into chemical energy.
Logistic growth
a type of growth whose rate starts out rapid and then levels off because of limiting factors which cause the population to reach a carrying capacity
Chromatid
one of two identical "sister" parts of a duplicated chromosome
Stroma
The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
ADP
(Adenosine Diphosphate) The compound that remains when a phosphate group is removed from ATP, releasing energy
Centromere
Area where the chromatids of a chromosome are attached
Community
all the different populations that live together in a certain area
Ecosystem
all the organisms that live in a place together with their nonliving or physical environment
Cell Cycle
series of events that cells go through as they grow and divide
NADPH
An electron carrier involved in photosynthesis. Light drives electrons from chlorophyll to NADP+, forming NADPH, which provides the high-energy electrons for the reduction of carbon dioxide to sugar in the Calvin cycle.
Deforestation
clearing or removal of trees
Interphase
period of the cell cycle between cell divisions
Cellular Respiration
Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen
Mitochondria
An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur.
Prophase
first and longest phase of mitosis, during which the chromosomes become visible and the centrioles separate and take up positions on the opposite sides of the nucleus
Trophic level
each of several hierarchical levels in an ecosystem, comprising organisms that share the same function in the food chain and the same nutritional relationship to the primary sources of energy
Biome
group of ecosystems that have the same climate and similar dominant communities
Metaphase
second phase of mitosis, during which the chromosomes line up across the center of the cell
Anaerobic Respiration
Respiration in the absence of oxygen. This produces lactic acid.
Greenhouse gas
a gas (carbon dioxide and chlorofluorocarbons) that contributes to the warming of the Earth by absorbing radiation
Anaphase
the third phase of mitosis, during which the chromosome pairs separate and move toward opposite poles
Glycolysis
A metabolic process that breaks down carbohydrates and sugars through a series of reactions to either pyruvic acid or lactic acid and release energy for the body in the form of ATP
Krebs Cycle (Citric Acid Cycle)
second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions
Telophase
the final phase of cell division, between anaphase and interphase, in which the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed.
Energy pyramid
a diagram that shows the amount of energy used and transferred between trophic levels
Limiting Nutrient or Factors
nutrient that is scarce or cycles slowly in an ecosystem
Cancer
disorder in which some of the body's cells lose the ability to control growth
Electron Transport Chain
a series of proteins in which the high-energy electrons from the Krebs cycle are used to convert ADP into ATP
Acid rain
rainfall that has become acidic because of atmospheric pollution (burning of coal and other fossil fuels); causes environmental harm
Centriole
Cell organelle that aids in cell division in animal cells only
Fermentation
Process by which cells release energy in the absence of oxygen, can be alcoholic or lactic acid.
Biomass pyramid
a diagram that shows the amount of organisms in a specific trophic level
Chromosome
a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
Aerobic Respiration
Respiration that requires oxygen
Nitrogen cycle
the series of processes by which nitrogen and its compounds are interconverted in the environment and in living organisms, including nitrogen fixation and decomposition
Crossing Over
Process in which homologous chromosomes exchange portions of their chromatids during meiosis.
Glucose
A simple sugar that is an important source of energy.
Non-native species/invasive species
any organism that is not from an area; can cause harm to that area
Nondisjunction
An error in meiosis or mitosis in which members of a pair of homologous chromosomes or a pair of sister chromatids fail to separate properly from each other.
Glycogen
Storage form of glucose in animals.
Lactic Acid
product of fermentation in many types of cells, including human muscle cells.
Biotic
The biological influences on organisms. Living part of the environment.
Abiotic
Physical components of an ecosystem. Nonliving part of the environment.
Endangered species
a species of animal or plant that is at a serious risk of extinction
Carbon Cycle
the series of processes by which carbon compounds are interconverted in the environment, involving the incorporation of carbon dioxide into living tissue by photosynthesis and its return to the atmosphere through respiration, the decay of dead organisms, and the burning of fossil fuels
Organism
A living thing; anything that can carry out life processes independently
Oxygen Cycle
the cycle that helps move oxygen through the three main regions of the Earth, the Atmosphere, the Biosphere, and the Lithosphere
Niche
An organism's particular role in an ecosystem, or how it makes its living.
Phosphorus Cycle
the process by which phosphorus moves through the lithosphere, hydrosphere, and biosphere
Habitat
Place where an organism lives
Hydrogen Cycle
the transmission of hydrogen from water to carbohydrates etc and back to water by living organisms
Nitrogen Fixation
the chemical processes by which atmospheric nitrogen is assimilated into organic compounds, especially by certain microorganisms as part of the nitrogen cycle
Keystone Species
a species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically.
Carrying Capacity
The largest population that an area can support.
Biodiversity
the variety of life in the world or in a particular habitat or ecosystem.
Biological Magnification
increasing concentration of a harmful substance in organisms at higher trophic levels in a food chain or food web
Invasive Species
plants and animals that have migrated to places where they are not native.
Passive Transport
the movement of substances across a cell membrane without the use of energy by the cell
Carbohydrates
Macromolecule made of carbon, Hyrdogen, and oxygen. Primary source of energy. Have a ratio of C:1; H:2, O:1
Cell
The basic unit of structure and function in living things
Active Transport
Energy-requiring process that moves material across a cell membrane against a concentration difference
Lipids
Energy-rich organic compounds, such as fats, oils, and waxes, that are made of carbon, hydrogen, and few oxygen.
Cell Theory
idea that all living things are composed of cells, cells are the basic units of structure and function in living things, and new cells are produced from existing cells
Eukaryote
A cell that contains a nucleus and membrane bound organelles
Glucose
A simple sugar that is an important source of energy. C6h12O6
Osmosis
Diffusion of water through a selectively permeable membrane
Diffusion
Movement of molecules from an area of higher concentration to an area of lower concentration.
Phospholipids
A molecule that makes up of the lipid bi-layer of cell membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail.
Prokaryote
A unicellular organism that lacks a nucleus and membrane bound organelles
Facilitated Diffusion
Movement of specific molecules across cell membranes through protein channels
cell membrane
the semipermeable membrane surrounding the cytoplasm of a cell. Regulates what enters and leaves the cell.
Animal Cell
does not have a cell wall or chloroplast and a small vacuole
Hypotonic
when comparing two solutions, the solution with the lesser concentration of solutes
fatty acids
Building Blocks (Monomer) of Lipids
Plant Cell
contains a cell wall, chloroplast and large vacuole
Endosymbiotic Theory
theory that eukaryotic cells formed from a symbiosis among several different prokaryotic organisms
Glycerol
Combines with fatty acids to make lipids.
Hypertonic
when comparing two solutions, the solution with the greater concentration of solutes
Isotonic
when the concentration of two solutions is the same
Monosaccharides
Simple Sugars like; glucose, fructose, galactose. Mono= one Saccharide= Sugar
Cell Wall
A rigid structure that surrounds the cell membrane and provides support to the cell.
Homeostasis
process by which organisms maintain a relatively stable internal environment
Monomer
A simple compound whose molecules can join together to form polymers
Nucleus
A part of the cell containing DNA and RNA and responsible for growth and reproduction.
Polymer
molecules composed of many monomers; makes up macromolecules
Cytoplasm
A jellylike fluid inside the cell in which the organelles are suspended. Outside the nucleus.
Polysaccharides
Carbohydrates that are made up of more than two monosaccharidesPoly= many Saccharide= Sugar
Nucleolus
Found inside the nucleus and produces ribosomes.
Glycogen
Polysaccharide, made up of long chains of glucose.
Organelle
A tiny cell structure that carries out a specific function within the cell.
Chitin
A polysaccharide, that makes up the cell walls of Fungi
Cell Membrane
A cell structure that controls which substances can enter or leave the cell.
Cellulose
Carbohydrate component of plant cell walls.
Chloroplasts
organelles that capture the energy from sunlight and convert it into chemical energy in a process called photosynthesis.
Starch
storage form of glucose in plants
Lysosome
An organelle containing digestive enzymes
Protein
An organic compound that is made of one or more amino acids and contains carbon, oxygen, hydrogen, and nitrogen. Builds muscle, tissues, enzymes, etc.
Golgi apparatus
A system of membranes that modifies and packages proteins for export by the cell.
Enzymes
proteins that act as catalysts (speed up chemical reactions).
Endoplasmic Reticulum
A system of membranes that is found in a cell's cytoplasm and that assists in the production, processing, and transport of proteins and in the production of lipids.
Catalyst
substance that speeds up the rate of a chemical reaction
Vacuoles
Cell organelle that stores materials such as water, salts, proteins, and carbohydrates.
nucleic acids
macromolecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus. Examples: DNA, RNA, ATP
Ribosomes
Is the site of proteins synthesis.
Nucleotide
monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base
Mitochondria
Powerhouse of the cell, organelle that is the site of ATP (energy) production.
amino acids
monomers or building blocks of proteins
Flagella
A long, whip-like filament that helps in cell motility. Many bacteria are flagellated, and sperm are flagellated.
RNA
ribonucleic acid; single-stranded nucleic acid that contains the sugar ribose
Cilia
Hairlike projections that extend from the plasma membrane and are used for locomotion.
DNA
deoxyribonucleic acid: double stranded nucleic Acid that contains deoxyribonucleic Acid.
Centromere
Area where the chromatids of a chromosome are attached
DNA
A complex molecule containing the genetic information that makes up the chromosomes. Made up of a double stranded nucleic acid that contains the sugar deoxyribose.
RNA
single-stranded nucleic acid that contains the sugar ribose
Nucleotide
monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base
Base Pairing
principle that bonds in DNA can form only between adenine and thymine and between guanine and cytosine
Deoxyribose
sugar found in DNA
Double Helix
two strands of nucleotides wound about each other; structure of DNA
Chromatin
Substance found in eukaryotic chromosomes that consists of DNA tightly coiled around histones
Genetic Code
the ordering of nucleotides in DNA molecules that carries the genetic information in living cells
Gene
A segment of DNA on a chromosome that codes for a specific trait.
Ribose
sugar found in RNA
DNA Polymerase
Enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule
Helicase
An enzyme that untwists the double helix of DNA at the replication forks.
Complementary Strand
A strand of DNA or RNA that has complementary bases to another strand of DNA or RNA. For instance, during DNA replication, the new strand that is formed is a complementary strand. (Complementary bases: A-T, C-G)
Semi-conservative
in each new DNA double helix, one strand is from the original molecule, and one strand is new
Replication Bubble
Segment of a DNA molecule that is unwinding and undergoing replication.
Messenger RNA
RNA molecule that carries copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell
Transfer RNA
type of RNA molecule that transfers amino acids to ribosomes during protein synthesis
Transcription
synthesis of an RNA molecule from a DNA template
Translation
Process by which mRNA is decoded and a protein is produced
Codon
A specific sequence of three adjacent bases on a strand of DNA that provides genetic code information for a particular amino acid
Anticodon
group of three bases on a tRNA molecule that are complementary to an mRNA codon
Protein
An organic compound that is made of one or more chains of amino acids and that is a principal component of all cells
Amino Acid
Building blocks of protein
Ribosome
Cytoplasmic organelles at which proteins are synthesized.
Classification
The process of grouping things based on their similarities
evolutionary classification
method of grouping organisms together according to their evolutionary history
Taxonomy
The scientific study of how living things are classified
binomial nomenclature
A system for giving each organism a two-word scientific name that consists of the genus name followed by the species name
Taxon
group or level of organization into which organisms are classified
Clade
A group of species that includes an ancestral species and all its descendants.
Levels of classification
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
Dichotomous key (classification key)
Classification tool used in identifying organisms or materials
Cladogram
A diagram that is based on patterns of shared, derived traits and that shows the evolutionary relationships between groups of organisms
Phylogeny
Evolutionary history of a species or group of species.
phylogenetic tree
A family tree that shows the evolutionary relationships thought to exist among groups of organisms based on evolutionary time
Endosymbiosis
A theorized process in which early eukaryotic cells were formed from simpler prokaryotes.
Chloroplast
An organelle found in plant and algae cells where photosynthesis occurs
Mitochondria
An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur.
Linnaeus
Swedish botanist who proposed the modern system of biological nomenclature (1707-1778)
Archaebacteria
kingdom of unicellular prokaryotes whose cell walls do not contain peptidoglycan
Eubacteria
Kingdom of unicellular prokaryotes whose cell walls are made up of peptidoglycan
Fungi
A kingdom made up of nongreen, eukaryotic organisms that have no means of movement, reproduce by using spores, and get food by breaking down substances in their surroundings and absorbing the nutrients
Plantae
Kingdom of multicellular photosynthetic autotrophs that have cell walls containing cellulose
Animalia
kingdom of multicellular eukaryotic heterotrophs whose cells do not have cell walls
Protista
Kingdom composed of eukaryotes that are not classified as plants, animals, or fungi
Virus
A tiny, nonliving particle that invades and then reproduces inside a living cell.
lysogenic cycle
a viral reproductive cycle in which the viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA
lytic cycle
a viral reproductive cycle in which copies of a virus are made within a host cell, which then bursts open, releasing new viruses