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Existing cells
Where do all cells come from?
Carrying Capacity
The maximum population of a particular organism that a given environment can support without detrimental effects
Gamete
a mature sexual reproductive cell, as a sperm or egg, that unites with another cell to form a new organism.
Zygote
the cell produced by the union of two gametes, before it undergoes cleavage.
Embryo
the young of a viviparous animal, especially of a mammal, in the early stages of development within the womb, in humans up to the end of the second month
Punnett Square
a type of grid used to show the gametes of each parent and their possible offspring; a type of grid that can indicate all the possible outcomes of a genetic cross
Phenotype
The expression of a specific trait based on genetic and environmental influences.
Genotype
the genetic makeup of an organism or group of organisms with reference to a single trait, set of traits, or an entire complex of traits.
Allele
any of several forms of a gene, usually arising through mutation, that are responsible for hereditary variation.
Homozygous
having identical pairs of genes for any given pair of hereditary characteristics
Heterozygous
having dissimilar pairs of genes for any hereditary characteristic
Dominant Trait
a trait that will appear in the offspring if one of the parents contributes it
Recessive Trait
a trait that mustt be contributed by both parents in order to appear in the offspring
Nondisjunction
the failure of chromosomes to separate and segregate into daughter cells at division
Mutation
a sudden change different than the parent type in one or more heritable characteristics, caused by a change in a gene or a chromosome
Genetic Engineering
the development and application of scientific methods, procedures, and technologies that permit direct manipulation of genetic material in order to alter the hereditary traits of a cell, organism, or population
Recombinant DNA
DNA in which one or more segments or genes have been inserted, either naturally or by laboratory manipulation, from a different molecule or from another part of the same molecule, resulting in a new genetic combination
Transcription
The process by which mRNA is synthesized from a DNA template resulting in the transfer of genetic information from the DNA molecule to mRNA
Replication
the process by which exact copies of complex molecules, such as DNA molecules, that occurs during growth of living organisms
Traslation
The process by which mRNA, tRNA, and ribosomes effect the production of a protein molecule from amino acids, the specificity of synthesis being controlled by the base sequences of the mRNA
Ecosystem
the interaction of a community of organisms with their environment
Producer
An autotrophic organism that serves as a source of food for other organisms in a food chain. Producers include green plants, which produce food through photosynthesis, and certain bacteria that are capable of converting inorganic substances into food through chemosynthesis
Anterior
The front surface of the body
Posterior
Near the tail end of the body
Chemoautotroph
an organism that depends on inorganic chemicals for its energy and principally on carbon dioxide for its carbon
Dichotomous Key
used to identify a plant or animal in which each stage presents descriptions of two distinguishing characters, with a direction to another stage in the key, until the species is identified
Binomial Nomenclature
a system for naming plants and animals by means of two Latin names: the first indicating the genus and the second the species to which the organism belongs
Autotroph
any organism capable of self-nourishment by using inorganic materials as a source of nutrients and using photosynthesis or chemosynthesis as a source of energy
Taxon
A taxonomic category or group, such as a phylum, order, family, genus, or species
chemosynthesis
the formation of organic material by certain bacteria using energy derived from simple chemical reactions
taxonomy
the science dealing with the description, identification, naming, and classification of organisms
Prokaryote
any cellular organism that has no nuclear membrane, no organelles in the cytoplasm except ribosomes, and has its genetic material in the form of single continuous strands forming coils or loops
Eukaryote
any organism having as its fundamental structural unit a cell type that contains specialized organelles in the cytoplasm, a membrane-bound nucleus enclosing genetic material organized into chromosomes, and an elaborate system of division by mitosis or meiosis
Exoskeleton
A hard, protective outer body covering of an animal, such as an insect, crustacean, or mollusk
Endoskeleton
The internal supporting framework of humans and other vertebrates, usually made of bone
Dorsal
Relating to or on the back or upper surface of an animal
Ventral
Relating to or on the front or lower surface of an animal
Aerobic Respiration
a type of respiration in which oxygen is taken in and carbon dioxide and water are produced
Anaerobic Respiration
an incomplete intracellular breakdown of sugar or other organic compounds in the absence of oxygen that releases energy; cellular respiration in the absence of oxygen
Pollution
The contamination of air, water, or soil by substances that are harmful to living organisms
Endotherm
a warm-blooded animal
Ectotherm
a cold-blooded animal
Commensalism
A symbiotic relationship in which one organism derives benefit while causing little or no harm to the other
Parasitism
A symbiotic relationship in which one organism benefits and the other is generally harmed
Mutualism
A symbiotic relationship in which each of the organisms benefits
Predation
A relationship between two species of animal in a community, in which one hunts, kills, and eats the other
Acid rain
rain that contains a high concentration of pollutants, chiefly sulphur dioxide and nitrogen oxide, released into the atmosphere by the burning of fossil fuels such as coal or oil
Biodiversity
The number, variety, and genetic variation of different organisms found within a specified geographic region
Habitat
The area or natural environment in which an organism or population normally lives
Biome
A large community of plants and animals that occupies a distinct region
Ovary
The part of a carpel or of a gynoecium made of fused carpels that contains the ovules in a flower
Adenine
A purine base that is a component of DNA and RNA, forming a base pair with thymine in DNA and with uracil in RNA
Thymine
A pyrimidine base that is a component of DNA. It forms a base pair with adenine
Guanine
A purine base that is a component of DNA and RNA, forming a base pair with cytosine
Cytosine
A pyrimidine base that is a component of DNA and RNA, forming a base pair with guanine
Uracil
A pyrimidine base that is a component of RNA, forming a base pair with adenine during transcription
Nucleotide
Any of a group of organic compounds composed of a nucleoside linked to a phosphate group
Phosphate
A salt or ester of phosphoric acid, containing the group PO 4
Messenger RNA
RNA that carries genetic information from the cell nucleus to the ribosomes where protein synthesis takes place
Transfer RNA
RNA that delivers the amino acids necessary for protein synthesis to the ribosomes
Anticodon
A sequence of three adjacent nucleotides in transfer RNA that binds to a corresponding codon in messenger RNA and designates a specific amino acid during protein synthesis
Codon
A sequence of three adjacent nucleotides on a strand of a nucleic acid that constitutes the genetic code for a specific amino acid that is to be added to a polypeptide chain during protein synthesis
Nucleus
An organelle in the cytoplasm of eukaryotic cells that contains nearly all the cell's DNA and controls its metabolism, growth, and reproduction
Ribosome
A sphere-shaped structure within the cytoplasm of a cell that is composed of RNA and protein and is the site of protein synthesis
Base Pairing
the hydrogen bonding that occurs between complementary nitrogenous bases in the two polynucleotide chains of a DNA molecule
Amino Acids
Any of a large number of compounds found in living cells that contain carbon, oxygen, hydrogen, and nitrogen, and join together to form proteins
Exponential Growth
a constant rate of growth applied to a continuously growing base over a period of time
Nitrogenous Base
One of the nitrogen-containing purines (adenine or guanine) or pyrimidines (cytosine, thymine, or uracil) found in the nucleic acids DNA and RNA
Biotic
Consisting of living organisms
Abiotic
Not associated with or derived from living organisms
Ecology
The scientific study of the relationships between living things and their environments
Biology
The scientific study of life and of living organisms
Zoology
The scientific study of organisms in the kingdom Animalia, including their growth and structure
Mitochondria
A structure in the cytoplasm of all cells except bacteria in which food molecules are broken down in the presence of oxygen and converted to energy in the form of ATP
Homeostasis
The tendency of an organism or cell to regulate its internal conditions, such as the chemical composition of its body fluids, so as to maintain health and functioning, regardless of outside conditions
Centriole
Either of a pair of cylinder-shaped bodies found in the centrosome of most eukaryotic organisms other than plants
Mitosis
the process by which the nucleus divides, in eukaryotic organisms, producing two new nuclei that are genetically identical to the nucleus of the parent cell
Meiosis
the process by which the nucleus divides in all sexually reproducing organisms during the production of spores or gametes
Asexual Reproduction
Reproduction in which offspring are produced by a single parent, without the union of reproductive cells
Sexual Reproduction
reproduction of organisms by the union of male and female reproductive cells
Protein Synthesis
the process by which individual amino acids are connected to each other in a specific order dictated by the nucleotide sequence in DNA
DNA
The nucleic acid that is the genetic material determining the makeup of all living cells and many viruses
Chromosome
A structure in all living cells that consists of a single molecule of DNA bonded to various proteins and that carries the genes determining heredity
Evolution
The process by which species of organisms arise from earlier life forms and undergo change over time through natural selection
Natural Selection
The process by which organisms that are better suited to their environment than others produce more offspring
Charles Darwin
English natural scientist who formulated a theory of evolution by natural selection
Speciation
The formation of new biological species by the development or branching of one species into two or more genetically distinct ones
Greenhouse Effect
The retention of part of the Sun's energy in the Earth's atmosphere in the form of heat as a result of the presence of greenhouse gases
Ecological Succession
the gradual and orderly process of change in an ecosystem brought about by the progressive replacement of one community by another until a stable climax is established
Energy Pyramid
a depiction of the amount of energy in each trophic level of an ecosystem
Consumer
A heterotrophic organism that feeds on other organisms in a food chain
Vacuole
A cavity within the cytoplasm of a cell, surrounded by a single membrane and containing fluid, food, or metabolic waste
Cell Wall
The outermost layer of cells in plants, bacteria, fungi, and many algae that gives shape to the cell and protects it from infection
Plasma membrane
The thin membrane that forms the outer surface of the protoplasm of a cell and regulates the passage of materials in and out of the cell
Endoplasmic Reticulum
An organelle consisting of a network of membranes within the cytoplasm of eukaryotic cells that is important in protein synthesis and folding and is involved in the transport of cellular materials
Mitochondria
A structure in the cytoplasm of all cells except bacteria in which food molecules are broken down in the presence of oxygen and converted to energy in the form of ATP
Chloroplast
A plastid in the cells of green plants and green algae that contains chlorophylls and carotenoid pigments and creates glucose through photosynthesis
Hypotonic
noting a solution of lower osmotic pressure than another solution with which it is compared
Hypertonic
noting a solution of higher osmotic pressure than another solution with which it is compared
Isotonic
noting or pertaining to a solution containing the same salt concentration as mammalian blood