Biology Final Exam Terms

Know these by heart

Meiosis

Meiosis is the 2 step cell division that creates four daughter cells, each with half the number of chromosomes, creating genetic diversity. It starts with one diploid cell, and ends with 4 haploid cells, and go through Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis twice.

Nondisjunction Meiosis I

Occurs when homologous chromosomes fail to separate during Anaphase I, cells 1+2 have too little chromosomes, while cells 3+4 have too many chromosomes.

Nondisjunction Meiosis II

Occurs when sister chromatids fail to separate during Anaphase II. Cells have 1+2 have the correct number of chromosomes, cells 3+4 has one too many, and too little.

Human Impact of Nondisjunction?

Leads to people having more of fewer chromosomes, resulting in genetic conditions like down syndrome, and turner syndrome.

Monsomy

The Zygote only has 2 pairs of chromosomes, not 3. It is missing a chromosome pair, and comes from the missing chromatid in the sperm.

Trisomy

Zygote only has 1 extra chromosome, which has 3 in one single pair. The egg is the one with the extra chromatid.

Complete dominance

One allele completely masks the other, so the heterozygote shows only the dominant trait.

X Linked Inheritence

A pattern of inheritance in which genes on the X chromosome are expressed more frequently in males because they have only one X chromosome.

Codominance

Both alleles are fully and equally expressed in the heterozygote without blending.

Incomplete Dominance

Neither allele is fully dominant, resulting in a blended or intermediate phenotype in the heterozygote.

Fossils

Preserved remains of dead organisms, shows how organisms have changed over time.

Comparative Anatomy

The study of morphology, (similarities and differences in body structures).

Embryology

The study of embryos, shows a common ancestor and how organisms start off similar but diverge differently to different forms

Molecular Biology

Study of DNA of organism., and the more similar the DNA sequence, more closely related the organisms.

Analogous structures

Has very different anatomies but similar functions. Seen in organisms that are not closely related but live in similar environments and have similar adaptations.

Ex.Butterfly and Bird

Show organisms evolving separately to best suit their environments. Shows how similar environmental stresses can cause similar evolutionary patterns 

Homologous structures

A homologous structure is a body part in different species that is similar because they came from a common ancestor, even though the body part may be used for different functions.

Ex.Front Forelimbs

Shows common ancestor, and how organisms started off with similar structures but evolved to better suit the environment.

Vestigial Structure

Anatomical remnants that were important in the organisms ancestors but are no longer used the same way

Ex. Wisdom Teeth, Appendix, Tailbone

Vestigial structures are evidence of evolution because they are leftover body parts that had a function in ancestors but are reduced or no longer useful, showing that species have changed over time.

Speciation

Occurs when populations of the same species stop interbreeding, and become genetically different, eventually being reproductive isolated, meaning they no longer have fertile offspring.

Genetic Drift

a random change in allele sequences in populations. It contributes to speciation by making them genetically distinct. It leads to speciation by the sequences changing overtime, and drifting genetically, which then RI occurs resulting in a new species.

Bottleneck Effect

An extreme example of genetic drift which occurs when a population declines to a very low number (usually by a catastrophe), then rebounds. This results in a loss of genetic diversity.

Founder Effect

Extreme genetic drift that occurs when a small sample of population settles in a location separate from the rest of the population. This results in a population with different alleles in a new population.

Mechanical Isolation

Is a type of reproductive isolating mechanism that prevents species from mating due to it’s incompatibility of physical structures.

Behavior Isolation

a type of reproductive isolating mechanism when 2 species are prevented from mating due to differences in mating behavior such as dances and songs

Ex. different bird calls for mating

Postzygotic Isolation

Occurs after fertilization altering the hybrids offspring survival and fertility.

Ex. a mule being infertile, weak, and dying very easily

Temporal Isolation

Is a type of reproductive isolation mechanism by preventing species from mating by their mating cycles occurring at different times.

Ex. a day owl and a night owl