Biology 9 Final Exam

End of year Biology Final

Homeostasis

The process by which an organism maintains a stable internal environment despite external changes (e.g., keeping your body temperature at around 98.6°F).

Negative Feedback

The primary mechanism for homeostasis where a stimulus triggers a response that counteracts or reverses the change to bring things back to a set point.

Digestive System Function

To take in nutrients, break down food, and get nutrients in to power the mitochondria.

Small Intestine

The major organ in the digestive system responsible for the absorption of nutrients.

Excretory System Function

To get metabolic waste out of the body (including food waste, sweat, urine, and CO2).

Nervous System Function

To take in and transmit electrical impulses

Reflex Arc

The structural unit of the nervous system responsible for immediate, automated homeostatic responses.

Surface Area to Volume Ratio

As cells grow, volume increases faster than surface area, reducing this ratio and making material exchange inefficient.

G1 Phase (First Gap)

The part of Interphase where the cell grows, accumulates nutrients, and prepares for DNA replication.

S Phase (Synthesis)

The part of Interphase where DNA replication occurs, resulting in the duplication of chromosomes into sister chromatids.

G2 Phase (Second Gap)

The part of Interphase where the cell continues to grow and checks for DNA errors, ensuring it is ready for division.

Prophase

First stage of mitosis where chromosomes condense, spindle fibers form, and the nuclear membrane breaks down.

Metaphase

Stage of mitosis where chromosomes line up perfectly in the middle of the cell.

Anaphase

Stage of mitosis where sister chromatids are pulled apart to opposite sides of the cell.

Telophase

Final stage of mitosis where two new nuclear membranes form around the separated chromosomes.

Cytokinesis

The division of the cytoplasm, resulting in two genetically identical daughter cells.

Structure of DNA

A double helix composed of two antiparallel strands with a sugar-phosphate backbone and nitrogenous bases paired by hydrogen bonds (C-G, A-T).

Helicase

The enzyme that "unzips" the DNA double helix during replication by breaking hydrogen bonds.

DNA Polymerase

The enzyme that joins individual nucleotides to produce a new strand of DNA and "proofreads" for errors.

Cyclins

Proteins that regulate the timing of the cell cycle.

Cancer

Uncontrolled cell division caused by a breakdown in cell cycle regulation mechanisms, leading to tumors.

Transcription

The process of copying a DNA gene into an mRNA strand inside the nucleus.

Translation

The process occurring at the ribosome where an mRNA message is translated into a chain of amino acids to build a protein.

mRNA (messenger RNA)

Takes genetic information from a gene and brings it to the ribosome.

tRNA (transfer RNA)

Brings the correct amino acid to the ribosome during translation.

rRNA (ribosomal RNA)

Makes up the physical and functional ribosomal site of protein synthesis.

RNA Polymerase

An enzyme that unwinds and unzips DNA to create a complementary mRNA copy during transcription.

Law of Dominance

Mendel's law stating that some alleles are dominant and can mask others (recessive).

Law of Segregation

Mendel's law stating that during gamete formation (meiosis), the two alleles for a gene separate so each gamete carries only one allele.

Law of Independent Assortment

Mendel's law stating that genes for different traits segregate independently when gametes are formed.

Haploid (n)

A cell having only one of each chromosome (half the diploid amount), typical of gametes.

Diploid (2n)

A cell having two of each homologous chromosome, typical of somatic body cells and zygotes.

Sister Chromatids

Two identical copies of a single chromosome formed during DNA replication (S phase) held together at the centromere.

Homologous Pairs

Chromosomes that possess the same genes in the same sequence and locations, one inherited from each parent.

Crossing Over

The process during meiosis when homologous chromosomes overlap and spontaneously trade sections, contributing to genetic diversity.

Incomplete Dominance

An inheritance pattern where the heterozygous phenotype is a distinct intermediate blend between the two homozygous phenotypes (e.g., pink flowers).

Codominance

An inheritance pattern where both alleles are fully and separately expressed in the phenotype (e.g., speckled chickens).

Multiple Alleles

An inheritance pattern where more than two alleles exist for a single gene, such as ABO Blood Typing.

Sex-Linked Inheritance

Genes located on the sex chromosomes (usually X)

Polygenic Inheritance

A trait controlled by two or more genes, each with multiple alleles, resulting in a continuous range of phenotypes (e.g., height, skin color).

Pedigree

A family tree chart used to track which members inherit a specific genetic trait across multiple generations.

Karyotype

A photograph of an individual's actual chromosomes grouped in homologous pairs to check for structural or numerical chromosomal disorders.

Human Chromosome Count

Humans have 46 chromosomes in total, arranged in 23 pairs.

Theory of Natural Selection

The mechanism of evolution consisting of Variation, Overpopulation, Struggle for Existence, and Differential Reproduction.

Homologous Structures

Features shared by distinct species that exhibit a similar anatomical design due to common ancestry, even if modified for different uses.

Analogous Structures

Features in different species that serve similar functions but evolved independently due to similar environments, not common ancestry.

Vestigial Organs

Remnants of ancestral structures that are no longer needed or functional in the modern organism (e.g., human appendix, whale pelvic bones).

Gene Pool

All the genes and collective alleles that are present in a specific population.

Directional Selection

Natural selection that favors individuals at one extreme of a phenotypic distribution curve, selecting against the other extreme.

Stabilizing Selection

Natural selection that favors moderate or intermediate traits, selecting against both phenotypic extremes.

Disruptive Selection

Natural selection that favors individuals at both extremes of a trait distribution, selecting against the moderate traits.

Speciation

The formation of a new species occurring when populations become reproductively isolated and can no longer produce fertile offspring.

Adaptive Radiation

When a single ancestral species rapidly evolves into many different forms that live in distinct ways (e.g., Darwin's finches).

Behavioral Isolation

Reproductive isolation caused by differences in mating rituals, calls, or courtship behaviors.

Geographic Isolation

Reproductive isolation caused by populations being separated by physical barriers like mountains, canyons, or rivers.

Temporal Isolation

Reproductive isolation occurring when populations breed or mate at entirely different times of the day, season, or year.

Macroevolution

Large-scale evolutionary patterns and processes that occur above the species level, such as mass extinctions or the origin of entire new biological classes.

Convergent Evolution

Unrelated organisms independently evolving highly similar traits because they adapted to similar environments (e.g., dolphins and sharks).

Coevolution

The process by which two species evolve in direct response to changes in each other over historical time.

Cladogram

A diagram showing evolutionary relationships based on lineages splitting from common ancestors and tracked via derived characteristics.

Derived Characteristic

A specific trait that appeared in the recent common ancestor of a lineage and was passed along to its descendants.