18,19,21,22 Organism Evolution, Classification & Development

Study.com College Biology 101

Phylogenetic Tree

Scientists use this chart to demonstrate the evolutionary relationships between different organisms. It can show changes related to evolutionary time and amounts of change.

Clade

This term refers to the groups made up of one ancestor and all of that creature's descendants that appear on phylogenetic trees and cladograms.

Postzygotic Barrier

This reproductive barrier works by lowering the ability of hybrid offspring of different organisms to reproduce.

Disruptive Selection

This type of natural selection occurs when organisms change based on negative pressures, such as if a bug eats one specific color of flower, leading to future generations of a different color.

Speciation

This process occurs when one species divides into at least two new species over a period of time. This can only occur if groups of the original species are removed from one another.

Acrosome

This part of a sperm cell acts as a cap and works to penetrate through the ovum's outer layers.

Heritability of Acquired Characteristics Theory

This theory has since been dismissed, but originally it asserted that an organism developed certain characteristics during its lifetime that it could pass to offspring.

Allopatric Speciation

This type of speciation is caused by a physical barrier separating the original species group. It can also be called geographic speciation.

Order of Taxonomic Classification

Kingdom and Phylum Class Order Family Genus and Species

Nondisjunction

This chromosome segregation error occurs when linked homologs, also called chromatids, fail to split apart during anaphase.

Ectoderm

Scientists use this term when referring to the outermost germ layer of cells in early embryos.

Convergent Evolution

This occurs when organisms individually evolve certain traits due to selective pressure, such as birds and bugs evolving wings, or creatures surrounded by water evolving to swim.

Endoderm

This is the innermost germ layer of cells in embryos. This layer will eventually develop into the gastrointestinal tract.

Type I Survivorship Curve

This kind of survivorship curve shows individuals surviving through middle life and then dying as they move to late life.

Oogenesis

the term for the biological process that results in the creation of ova (female gametes)

Clades: Major Types

Monophyletic Paraphyletic Polyphyletic

Sympatric Speciation

This kind of speciation happens even when organisms are still located in close physical proximity.

Polyploidy

This is a characteristic that can allow sympatric speciation. It only occurs in organisms or cells that possess more than two full sets of chromosomes.

Cladogram

This type of chart can help determine how closely related one creature is to another. Organisms that are more closely related should be grouped closer together.

Mesoderm

This is the middle germ layer of early embryo cells.

Type II Survivorship Curve

This type of survivorship curve indicates that a species has a constant mortality rate across its lifespan.

Natural Selection: Major Types

Directional Disruptive Stabilizing

Prezygotic Barrier

a type of barrier that halts reproduction by stopping fertilization from ever occurring

Characteristic shared by prezygotic and postzygotic barriers

Both of these barriers will isolate species.