Biology Air Test - 2025

Study Guide

Ecology : Levels of Organization

Population - All of the same species living in a particular area

Community - All of the living things ( different species ) living in a particular area

Ecosystem - Community living things plus their non-living surroundings

Natural Selection

Organism that are best adapted for their environment have the highest fitness and therefore survive, reproduce, and pass on their good gene to their offspring

Sexual Selection

Females choose males based on sexy or showy phenotype or behaviors

Gene Flow

When individuals move into or out of a population, new allele/genes/traits are added to or removed from the mating gene pool

Genetic Drift

Random change in gene frequency within a population due to random events. ( Natural disaster ). Only the survivors of a disaster can reproduce, and only gene of the survivors can be passed on.

Evidence for evolution

Fossils and Comparative anatomy - If two species share lots of physical similarities, they are probably related.

Biomolecules - Compare DNA, RNA, or amimo acids. if the molecules have few differences, then they are probably related. More differences = less related

Ecology: Cause and Effect in Ecosystems

Biomagnification/Bioaccumulation - If pollutant is taken up by producers, then the relative amount of that pollutant will increase moving up the food chain. Top-level consumers are often most affected by these pollutants.

Algal Blooms - Extra fertilizer wash into lake or ponds; algae take up extra nutrients and overpopulate; algae start dying off and decomposers eat them; decomposers increase in number and suck all the oxygen out of the water

Carrying capacity - the number of organism in a population that the ecosystem can support. Usually hovers around an average number. If population too large - run out of food, population drops. If population small - predators run out of food population rises.

Cladograms

Diagrams that show evolutionary relationships between organisms

1. Organism shown before a trait mark Do Not have that trait. Organism shown after a trait mark do have that trait.

2. Organisms who are closer together on a cladogram shared a more recent ancestor and are therefore more closely related.

Prokaryotes

No nucleus, Cell membrane, Cell wall, and ribosomes

Eukaryotes

Nucleus, mitochondria, chloroplasts, Endoplasmic reticulum, golgi

Cell Structures

Nucleus - Contains DNA

Cell wall - Extra support/protection around plants and bacteria cells

Ribosomes - Make protein

Mitochondria - break down glucose to release energy

Chloroplast - carries out photosynthesis in plant cells

Enzymes

1. Every enzyme helps ONE reaction and binds to ONE substrate (starting material)

2. Shape is very important. If the shape changes, enzyme is denatured and can’t bind to substrate

3. Work best at certain temperature and pH. If too hot or too acidic/basic denaturation (shape changes, reaction slows and then stops)

Cell Transport/Cell Membrane

Diffusion - Movement of smal uncharged particles from high to low concentration, does not need energy, does not use a protein channel

Osmosis - Diffusion of water molecules, does not need energy

Facilitated diffusion - Bigger molecules like proteins or sagas go through a protein channel

Active transport - Mostly charged particles get pumped across the membrane: need energy

Biomolecules

Carbs - energy sources like sugars and starches

Lipids - Fats and oils. Make up the cell membrane and store extra energy

Proteins - Building blocks of body (muscles, hair, and bones) or enzymes that speed up reactions in the body

Nucleic Acids - carry genetic information (DNA, RNA)

Photosynthesis

Occurs in the chloroplast - Chlorophyll - Green Pigment

6CO2 + 6H2O + light ——> C6H12O6 + 6O2

Cellular Respiration

Occurs in Mitochondria

C6H12O6 + 6O2 ——> 6O2 + 6H2O + 36 ATP (stores energy for the cell)

Chromosomes

46 ( 44 autosomal 2 sex )

Gene

Segment of DNA that codes for a particular protein

Alleles

Different forms of gene (Dominant allele, Recessive)

genotype

Allele combination - Genetic makeup

Phenotype

Physical trait determined by genotype

Punnett square

Diagram used to predict genotype and phenotype ratio of offspring

Pedigree

Family tree diagram that shows inheritance of a trait through multiple generations.

Gene linkage

Two genes are located close together on the same chromosome

Cell division

Mitosis - Body cells, Identical copies of themselves. Produce 2 daughter cells, necessary for growth, healing, and repair.

Meiosis - Makes gametes. Half the number of chromosomes is accomplished at fertilization. Produce 4 genetically different daughter cells. Is nessacary for the production of sperm and eggs for sexual reproduction

Complete dominance

Mendelian inheritance - Normal dominant/recessive; dominant masks recessive

Sex linked trait

Trait carried on a sex chromosome; X-linked recessive most common

Incomplete dominance

Three phenotypes instead of two (Heterozygote has mixed/blend phenotype)

Polygenic trait

Trait determined by more than one gene

Epistasis

One gene changes or masks the result of another gene

Pleiotropy

One gene affects more than one phenotype/part of the body

DNA and RNA

DNA - Two strand, uses based GCAT, stays in necleus

RNA - One strand, uses bases GCAU, starts in nucleus

mRNA - Messenger RNA. Carries instructions from DNA to ribosomes. Made during transcription in the nucleus

tRNA - transfer RNA. Bring animos acid to ribosomes during translation

rRNA - Ribosomal RNA make up ribosome

Gene Regulation and Expression

Cell differentiation - different types of cell have different gene expressed because they have different/function within the body

Stem cells - not yet differentiation, have many possible pathways of differentiated

Protein Synthesis

Transcription - Rewriting DNA into an mRNA messenger. Takes place in nucleus

Translation - mRNA travels to ribosome amino acids are strung together to create a protein

Mutations

Changes in DNA or RNA structure/ sequence

Point mutation - one base substituted for another

Frameshift - base added or deleted; disrupts entire protein downstream from mutation

Gene Technology

Cloning - Make an identical copy of an organism

Restriction enzymes - cut DNA at specific base sequence

Gel electrophoresis - create a DNA fingerprint

Genetic Engineering - purposefully changing DNA within an organism, or adding/removing gene to an organism’s genome

Gene therapy - Introduce a gene into a patient’s cells if the patient’s own gene is not function. Gene that’s added will produce protein that has been mission since patient’s own gene is malfunctioning

DNA vaccines - Expose immune system to DNA of a germ without actually causing illness; Immune system creates antibodies that will recognize the real germ if you come into contact with it