Biology MCAS Stuff to Study

Theory of Evolution

Due to the unequal ability of individuals to survive and reproduce, populations gradually change over time. Favorable characteristics accumulate over generations, and new species may arise.

Common Descent with Modification

The process by which species of living things can undergo modification over time, with such change sometimes resulting in the formation of new, separate species

Natural Selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits. The surviving organisms survive, reproduce, and pass on those favorable characteristics to the new generation.

Fitness

The ability of an organism to survive and reproduce

Adaptation

An inherited trait that increases an organism's chance to survive and reproduce

Natural variation

differences among individuals of a species; results from mutation and genetic shuffling during sexual reproduction (half of the chromosomes come from mom and half from dad)

Artificial selection

Humans breed organisms with specific traits in order to produce offspring with identical, specific traits.

Evidence for Evolution (5 things)

• Fossil Record (shows how organisms changed over time)
• Distribution of species (species adapted to their environment)
• Homologous body structures/comparative anatomy (species inherit traits from a common ancestor, more similar structures , the more related they are)
• Embryology (the more similar their embryos, the more related they are)
• Similarities in molecular sequences (DNA, amino acids)

How are fossils evidence for evolution?

Show physical changes in species over time

How is distribution of species evidence for evolution?

Organisms adapted to their geographic location over time, but descended from a common ancestor

How are homologous structures evidence for evolution?

When new species arose from a common ancestor, the composition of certain body parts are similar (like the types of bones found in limbs of animals), but the form changed over time to accommodate for the adaptations and functions the organism needs to perform

How are embryos evidence for evolution?

Closely related organisms have very similar structures throughout embryo development, showing the similarities between types of cells in animals

How are DNA and amino acids used as evidence for evolution?

The more similar the DNA sequence or sequence of amino acids, the more closely two organisms are.

Species

A group of organisms that are so closely related that they breed with one another and produce fertile offspring.

Types of Isolation (which can lead to the formation of a new species)

Behavioral (different mating behaviors), Geographic (different locations/physically separated), Temporal (different timing of reproduction)

Directional Selection

occurs when natural selection favors one of the extreme variations of a trait

Stabilizing Selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

Disruptive Selection

favors individuals at both extremes of the phenotypic range

Classification/Taxonomy

The process of grouping organisms based on their common ancestry

Binomial Nomenclature

Two-word scientific name for a species (Genus species)

Taxon

The category into which related organisms are placed (example: Class Mammalia)

Hierarchy of Taxonomy (most inclusive/broadest to most specific)

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Two organisms are closely related if they share (many or few?) taxa

Many

Cladogram

Diagram that shows the evolutionary relationships among a group of organisms

Speciation

Evolutionary process when new species arise

Mendel's Findings in F1 when crossing two contrasting traits

Only one trait (dominant) appeared in the offspring

Mendel's findings in F2 when crossing F1

The dominant trait from F1 appears 75% of the time, the other trait (recessive) appears 25% of the time

Genes

Sections of DNA that code for traits (ex: hair color is a gene)

Alleles

Different forms of a gene (ex: black, brown, red, blonde are all alleles - versions - of the hair color gene). People inherit two alleles for every gene, one from each parent.

Dominant allele

An allele whose trait always shows up in the organism when the allele is present. Typically represented by a capital letter. (ex: if black is the dominant hair color, as long as one of their two alleles for hair color is the black hair allele, the person will have black hair. Represented by B)

Recessive allele

An allele that is hidden whenever the dominant allele is present. Typically represented by a lowercase letter. (ex: if blonde is the recessive hair color, someone needs to inherit two blonde alleles in order to have blonde hair. Represented by b)

Homozygous (aka "pure")

A term for an organism with two of the same alleles for a trait. Ex: two dominant (BB) or two recessive (bb).

Heterozygous (aka "hybrid")

A term for an organism with two different alleles for a trait. Ex: one dominant and one recessive (Bb).

Genotype

An organism's genetic makeup, or allele combinations. The letters used to describe an organism's traits. Ex: BB, bb, or Bb.

Phenotype

An organism's physical appearance, or visible traits. Ex: black hair, blonde hair, etc.

Practice Punnett Square for two pea plants.
Yellow is dominant and green is recessive.
Cross a green pea with a heterozygous yellow pea.
Determine the possible phenotypes and genotypes of the offspring.

See image!
Parents: yy x Yy
Offspring: 50% yellow (Yy), 50% green (yy)

Outcome of the following dihybrid cross:
Homozygous dominant for two traits (RRYY) and homozygous recessive for two traits (rryy)

Each offspring will be heterozygous for both traits (RrYy) and will display the dominant phenotypes for both traits.

Phenotype outcome of the following dihybrid cross:
Two parents who are heterozygous for two traits
(RrYy x RrYy)

9:3:3:1 Ratio - always!
9 of 16 will be dominant for both traits
3 of 16 will be dominant for trait 1, recessive for trait 2
3 of 16 will be recessive for trait 1, dominant for trait 2
1 of 16 will be recessive for both traits

Incomplete dominance

Inheritance pattern where the heterozygous phenotype is a blend between two alleles. Neither allele is dominant or recessive. Different letters are used to represent the alleles. (Example: RR = red flowers, WW = white flowers, RW = pink flowers)

Codominance

Inheritance pattern where the heterozygous phenotype shows both traits of two alleles. Neither allele is dominant or recessive. Different letters are used to represent the alleles. (Example: RR = red fish, BB = blue fish, RB = red and blue fish)

Multiple alleles

Trait where there are 3 or more alleles (versions of the gene). Creates more possible phenotypes. *Organisms still only inherit 2 alleles because they get one from each parent.

Polygenic traits

Traits controlled by two or more genes. Creates a range of phenotypes rather than distinctly separate genotypes. Examples: hair color, skin color , eye color

Sex-linked (or X-linked) traits

Genes that are found on the X chromosome.
*Recessive traits are more common in males because they only need to inherit 1 recessive allele on their singly X chromosome, while females need to inherit 2 recessive alleles in order to have the trait.

Male genotype

XY

Female genotype

XX

Blood Types

A multiple allele/codominant trait.
Possible alleles: IA, IB, i
Possible blood types: A, B, AB, or O

Pedigree

A diagram that shows the occurrence of a genetic trait in several generations of a family. Squares are males, circles are females, colored-in shapes means the person has the trait, children stem between a male and a female.

How many chromosomes do humans have?

46 chromosomes (23 from each parent)

Nondisjunction

Abnormal number of chromosomes in cells, resulting in a genetic disease. (Example: down syndrome results from having 3 copies of chromosome number 21)

Homeostasis

the balanced, steady state that your body maintains to keep you healthy; all of your cells and organs systems work together to maintain this

Function of the Brain

Brain processes and analyzes information from sensory neurons and determines a response to send down a motor neuron.

Sensory Neuron

neurons that carry incoming information from the sensory receptors (information about a stimulus) to the brain and spinal cord (CNS)

Motor Neuron

neurons that carry outgoing information (a response) from the brain and spinal cord (CNS) to muscles and glands

Neurotransmitter

A chemical that passes the message from one neuron to the next (by moving across the synapse-gap)

Nervous System

the body's speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous systems

Conscious Pathway

Information has to travel to and from the BRAIN. The brain processes a nerve impulse from a sensory neuron and sends directions for response to motor neurons

Unconscious Reflex Pathway

Fast because information does not need to travel to the brain; it only has to travel to and from the SPINAL CORD. Sensory neuron impulses travel directly to the spinal cord, then to motor neurons without the input of the brain

Endocrine System

the body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream

Hormones

Chemical messengers (made of lipids or proteins) that travel in the blood to send signals to different tissues in the body

Liver (ALL Functions)

Digestive System Function-produces bile

Excretory System Function-filters blood and breaks down toxins

Endocrine System Function-Stores sugar as glycogen in response to insulin hormone; release sugar into the blood in response to glucagon hormone

Kidneys

Kidneys remove waste products (including urea) and water from the blood to make urine.

Digestive System

Breaks down food into absorbable units that enter the blood for distribution to body cells.

Excretory System

the system that removes waste from your blood and controls water and salt balance

Chemical Reaction

process that changes substances into different substances by breaking and forming chemical bonds

Reactants

Substances that go into chemical reactions

Products

Substances that are formed by a chemical reaction

Catalyst

Anything that speeds up a chemical reaction

Enzyme

A protein that speeds up a chemical reaction

Substrate

A reactant in an enzyme reaction

Active site

The location where the substrate binds to an enzyme

Activation energy

The energy needed to get a chemical reaction started

pH and Temperature's Effect on Enzyme Activity

Acidic and basic pH levels denature (unravel, deform) the enzyme, so the substrate cannot fit in the active site, and the rate of reaction decreases

Denature

A change in the shape of a protein (usually an enzyme) that can be caused by changes in temperature or pH

Villi

Projections on the inside of the small intestine that increase the surface area for absorption of nutrients

Peristalsis

Muscle contractions that move food and waste through the esophagus and intestines

Mouth

Where chemical (saliva) and mechanical (teeth/chewing) digestion begins

Esophagus

Tube connecting the mouth to the stomach

Stomach

The organ that stores food, kills bacteria, and breaks down food (with hydrochloric acid) and protein (with pepsin enzyme)

Small Intestine

The organ connected to the stomach that continues to digest food (with enzymes and bile from accessory organs) and absorbs nutrients

Large Intestine

The organ connected to the small intestine that reabsorbs water from waste

Rectum

The organ connected to the large intestine that stores waste before it is eliminated from the body

Pancreas

An accessory organ that produces enzymes to help digest food in the small intestine

Liver

An accessory organ that produces bile to help digest fats in the small intestine

Gall bladder

An accessory organ that stores bile that was produced by the liver

Amylase

An enzyme (in saliva and made by the pancreas) that breaks down carbohydrates

Trypsin

An enzyme (made by the pancreas) that breaks down protein

Pepsin

An enzyme (made in the stomach) that breaks down protein

Lipase

An enzyme (made in the pancreas) that breaks down lipids (fats)

Bile

A chemical produced by the liver that breaks down lipids (fats)

Functions of the circulatory system

• Transport nutrients throughout the body
• Get rid of wastes
• Control body temperature

Pulmonary circulation

flow of blood from the heart to the lungs and back to the heart

Systemic circulation

circulation that supplies blood to all the body except to the lungs

Arteries

Blood vessels that carry blood away from the heart

Veins

Blood vessels that carry blood back to the heart

Capillaries

Smallest vessels where the blood exchanges nutrients and wastes with the cells of the body

Atherosclerosis

Condition where fatty deposits (plaque) build up on the inner walls of the arteries. Sign of heart disease.

Heart attack

a condition in which blood flow to part of the heart muscle is blocked, causing heart cells to die

Stroke

Damage to the brain from interruption of its blood supply (typically blood clot)

Function of blood

Transports nutrients, oxygen, carbon dioxide, waste products, hormones to and from cells, regulates body temperature, protects against bacteria and viruses

Red blood cells

Transport oxygen. Most numerous blood cell.