Bio Unit 7

Ingestion

The act of eating; the first stage of food processing in animals.

Blastula

An embryonic stage that marks the end of cleavage during animal development; a hollow ball of cells in many species.

Gastrula

The embryonic stage resulting from gastrulation in animal development. Most animals have one made up of 3 layers of cells: ectoderm, endoderm, and mesoderm.

Endoderm

The innermost of 3 embryonic cell layers in a gastrula; gives rise to the innermost linings of the digestive tract and other hollow organs in the adult.

Ectoderm

The outer layer of 3 embryonic cell layers in a gastrula. It forms the skin of the gastrula and gives rise to the epidermis and nervous system in the adult.

Mesoderm

The middle layer of the 3 embryonic cell layers in a gastrula. It gives rise to muscles, bones, the dermis of the skin, and most other organs in the adult.

Larva

A free-living, sexually immature form in some animal life cycles that may differ from the adult in morphology, nutrition, and habitat.

Metamorphosis

The transformation of a larva into an adult.

Heredity

The transmission of traits (inherited features) from one generation to the next.

Genetics

The scientific study of heredity.

Character

A heritable feature that varies among individuals within a population, such as flower color in pea plants or eye color in humans.

Trait

A variant of a character found within a population, such as purple or white flowers in pea plants.

True-breeding

Referring to organisms for which sexual reproduction produces offspring with inherited traits identical to those of the parents. The organisms are homozygous for the characters under consideration.

Hybrid

Offspring that results from the mating of individuals from 2 different species or from 2 true-breeding varieties of the same species; an offspring of 2 parents that differ in 1 or more inherited traits; an individual that is heterozygous for 1 or more pairs of genes

Cross

A mating of 2 sexually reproducing individuals; often used to describe a genetics experiment involving a controlled mating (a “genetic cross”).

P (parental) generation

The parent individuals from which offspring are derived in studies of inheritance

F1 (first filial) generation

The offspring of 2 parental (P generation) individuals.

F2 (second filial) generation

The offspring of the F1 generation.

Allele

An alternative version of a gene.

Homozygous

Having 2 identical alleles for a given gene.

Heterozygous

Having 2 different alleles for a given gene.

Dominant allele

The allele that determines the phenotype of a gene when the individual is heterozygous for that gene.

Recessive allele

An allele that has no noticeable effect on the phenotype of a gene when the individual is heterozygous for that gene.

Law of segregation

A general rule in inheritance that individuals have 2 alleles for each gene and that when gametes form by meiosis, the 2 alleles separate, each resulting gamete ending up with only 1 allele of each gene.

Punnett square

A diagram used in the study of inheritance to show the results of random fertilization.

Phenotype

The expressed traits of an organism.

Genotype

The genetic makeup of an organism.

Locus

The particular site where a gene is found on a chromosome.

Monohybrid cross

An experimental mating of individuals that are heterozygous for the character being followed (or the self-pollination of a heterozygous plant).

Dihybrid cross

An experimental mating of individuals that are each heterozygous for both of 2 characters (or the self-pollination of a plant that is heterozygous for both characters).

Law of independent assortment

A general rule of inheritance, originally formed by Gregor Mendel, that when gametes form during meiosis, each pair of alleles for a particular character segregates independently of other pairs. Aka Mendel’s second law of inheritance.

Testcross

The mating between an individual of unknown genotype for a particular character and an individual that is homozygous recessive for that same character. It can be used to determine the unknown genotype (homozygous dominant vs. heterozygous).

Rule of multiplication

A rule stating the probability of a compound event is the product of the separate probabilities of the independent events.

Rule of addition

A rule stating the probability that an event can occur in 2 or more alternative ways is the sum of the separate probabilities of the different ways.

Pedigree

A family genetic tree representing the occurrence of heritable traits in parents and offspring across a number of generations. It can be used to determine genotypes of matings that have already occurred.

Huntington’s disease

A human genetic disease caused by a single dominant allele; characterized by uncontrollable body movements and degeneration of the nervous system; usually fatal 10-20 years after the onset of symptoms.

Complete dominance

A type of inheritance in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable.

Incomplete dominance

A type of inheritance in which the phenotype of a heterozygote is intermediate between the phenotypes of the 2 types of homozygotes.

Embryonic layers

The middle embryonic germ layer, between the ectoderm and endoderm, from which connective tissue, muscle, bone, cartilage, and blood vessels develop.

Segmented body parts

Segmented things are divided into separate parts, and segmented animals have bodies made up of distinct sections. An earthworm is one example of a segmented animal. Although humans clearly aren't segmented the way worms and leeches are, we do have segmented spinal columns, with repeated segments, or vertebrae.

Coelom

the fluid-filled body cavity of an animal that contains the internal organs (as the heart, lungs, and kidneys)

Induction

process by which the presence of one tissue influences the development of others. Certain tissues, especially in very young embryos, apparently have the potential to direct the differentiation of adjacent cells.

Cell migration

the directed movement of a single cell or a group of cells in response to chemical and/or mechanical signals.

Programmed cell death

less technical term for apoptosis. the death of cells which occurs as a normal and controlled part of an organism's growth or development.

Pleiotropy

Pleiotropy occurs when one gene influences two or more seemingly unrelated phenotypic traits. Such a gene that exhibits multiple phenotypic expression is called a pleiotropic gene.

Polygenic inheritance

the inheritance of a trait governed by more than one genes