Lesson: Chapter - 11

Q-T

R

Refers to an allele that cannot control the phenotype unless it is the only kind of allele present, as in a homozygote or hemizygote. Also refers to the trait or phenotype produced when only a recessive allele is present. The opposite of recessive is dominant.

The inability of individuals within a species to create offspring with members of any other species. The mark of a species is its reproductive isolation from all other species.

The organ system responsible for the intake of oxygen and diffusion of that gas into the blood and the elimination of carbon dioxide from the body. Important structures of the system are the pharynx, larynx, trachea, bronchi, bronchioles, and lungs. Alveoli in the lungs are the location of gas exchange with the blood. The movement of the muscular diaphragm allows the lungs to inhale and exhale.

One type of nucleic acid polymer. RNA nucleotides’ sugars contain one more oxygen atom than DNA nucleotides’ sugars. RNA nucleotides can have the nitrogenous bases adenine, cytosine, guanine, and uracil.

Organelle responsible for protein synthesis. Ribosomes are located in cytoplasm or endoplasmic reticulum.

The part of a plant beneath the soil; responsible for collecting water and minerals from the soil, storing nutrients, and securing the plant to the ground. Can be fibrous or a taproot.

An outgrowth of a plant root that provides an increased surface area for the absorption of water and dissolved minerals from the soil.

Slender horizontal stem that can form new plants via specialized nodes.

S

See decomposers.

Mendel’s conclusion that individuals have two copies of each gene, and that these copies separate randomly during gamete formation, one copy per gamete. This law is true except for genes on sex chromosomes in males, who have only one copy of each such gene. It is often called Mendel’s first law.

Fluid-filled structure within the ear that can detect balance.

Green, leaflike structure that encloses and protects the unopened flower bud.

See gamete.

Refers to a chromosome involved in defining the sex of an individual. Humans have two sex chromosomes and 44 autosomes. In females, both sex chromosomes are X chromosomes. Males have one X chromosome and one Y chromosome.

Refers to a gene located on a sex chromosome or to a trait defined by such a gene. Such traits will appear with different frequencies in males and females, and males and females will differ in their ability to transmit the trait to their offspring. In order for a recessive sex-linked trait such as hemophilia or color blindness to manifest in the phenotype of a woman, it must be inherited from both mother and father; such diseases will be present in the phenotype of a man if he inherits it just from his mother.

Any plant or animal cell that is not a germ cell, meaning it is not passed down to offspring. The class of cell formed during mitosis.

One half of the motor system of the peripheral nervous system. Responsible for voluntary, or conscious, movement. Neurons in this system target skeletal muscles and release the neurotransmitter acetylcholine.

The development of a species through evolution. A species forms when its members become reproductively isolated from all other organisms. Speciation can occur through geographic separation that eliminates gene flow or through adaptive radiation.

A group of organisms defined by their ability to interbreed with only each other.

The male gamete in sexual reproduction.

The process in which haploid sperm cells form through meiotic division.

A long cylinder of nervous tissue that extends along the vertebral column from the head to the lower back. It controls some autonomic responses and connects the brain to the peripheral nervous system.

Usually unicellular and microscopic, spores are produced by protist molds, fungi, and plants and are able to develop into new individuals. Spores are able to survive without food or water for long periods. Most fungi spend part of their life cycle as hyphae and part as spores.

A diploid plant or plant structure that produces haploid spores through meiosis.

When selection pressures favor the average form of a trait.

The male reproductive organ of the flower, consisting of an anther and filament.

The top part of the pistil, where pollen grains are received.

Small epidermal pores, surrounded by two guard cells, through which gases diffuse and water transpires in and out of a leaf.

A codon on mRNA that signals the termination of DNA translation. There are three stop codons: UAA, UAG, or UGA.

The shaft of the pistil that leads from the stigma down into the ovary.

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