Key concepts for Living Environment Regents Exam

Centrifuge

A centrifuge separates material according to density.

Gel electrophoresis

Gel electrophoresis uses electricity to separate DNA fragments.

Indicator

An indicator changes color in the presence of a specific substance.

Microscope images

Images under a microscope always appear upside down and backwards.

Field of view under high power

Under high power, the field of view is smaller.

Image brightness under scanning power

An image is brighter under scanning power.

Hypothesis

A hypothesis must be written as a statement.

Independent variable

The one factor that is changed in an experiment is the independent variable.

Dependent variable

The dependent variable is what is being measured.

Control group

The control group is the group used as a standard for comparison.

Constant variable

A constant variable is kept the same in all groups.

Valid experiment

A valid experiment has a large sample size, only one independent variable, and is repeated.

Organic compounds

Organic compounds must contain both carbon and hydrogen.

Building blocks of lipids

The building blocks of lipids are 1 glycerol and 3 fatty acids.

Starches

Starches are made of simple sugars (monosaccharides like glucose).

Nucleotide

A nucleotide contains a phosphate, sugar, and nitrogen base.

Proteins

Proteins are made of amino acids.

Protein shape and function

The shape of a protein determines its function.

Enzymes

Enzymes are a type of protein.

Synthesize

To synthesize means to build a larger molecule.

Digest

To digest means to break down molecules.

Catalyst

A catalyst is an enzyme that speeds up reactions and can be reused.

Lock and key model

The lock and key model shows that enzymes have specific shapes that fit specific substrates.

Temperature and pH

Temperature and pH affect enzyme function.

Photosynthesis

Photosynthesis occurs in the chloroplast and uses CO₂, water, and sunlight to make glucose and oxygen.

Cellular respiration

Cellular respiration uses O₂ and glucose to produce CO₂, water, and ATP.

Metabolism

Metabolism is the sum of all life processes.

Regulation

Regulation involves the control and coordination of life activities.

Reproduction

The life function not needed by individuals but necessary for a species is reproduction.

Homeostasis

Homeostasis maintains internal stability.

Failure of homeostasis

Failure of homeostasis can result in illness or death.

Levels of organization

Levels of organization: molecule → organelle → cell → tissue → organ → organ system → organism.

Prokaryotic cells

Prokaryotic cells lack a nucleus and membrane-bound organelles.

Eukaryotic cells

Eukaryotic cells have a nucleus with DNA.

Nucleus

The nucleus is the cell's control center.

Ribosomes

Ribosomes are the site of protein synthesis.

Mitochondria

Mitochondria carry out cellular respiration and make ATP.

Plant cells

Plant cells have chloroplasts and a cell wall.

Cell membrane

The cell membrane is selectively permeable.

Phospholipid bilayer

The cell membrane is made of a phospholipid bilayer and proteins.

Diffusion

Diffusion moves materials from high to low concentration without energy.

Active transport

Active transport moves substances against a concentration gradient and requires energy.

Nutrient absorption

Nutrient absorption occurs in the small intestine.

Villi

Villi increase the surface area for absorption.

Arteries

Arteries carry blood away from the heart.

Capillaries

Capillaries are thin vessels where diffusion occurs.

Nervous and endocrine systems

The nervous and endocrine systems carry out regulation.

Neurotransmitters

Neurotransmitters are chemicals that help nerve cells communicate.

Insulin and diabetes

Lack of insulin causes diabetes.

Negative feedback

Negative feedback helps maintain homeostasis (e.g., insulin and blood sugar).

Asexual reproduction

Asexual reproduction involves one parent, uses mitosis, and creates identical offspring.

Sexual reproduction

Sexual reproduction involves two parents, uses meiosis, and creates genetic variation.

Mitosis

Mitosis = 1 division, makes 2 diploid cells, used for growth and repair.

Meiosis

Meiosis = 2 divisions, makes 4 sperm or 1 egg, used for sexual reproduction.

Gametes

Gametes unite to form a zygote with 46 chromosomes (2n).

Differentiation

The process that forms specialized cells.

Estrogen and Progesterone

Female hormones made in the ovaries.

Fertilization

Occurs in the oviduct; the embryo develops in the uterus.

Placenta

The site of diffusion between mother and fetus.

Gene

A section of DNA that codes for a protein.

DNA Pairing

In DNA, A pairs with T, and C pairs with G.

Trait

A characteristic determined by a gene.

DNA Replication

Semi-conservative—each new strand has one original and one new half.

Clone

An organism that is genetically identical to the donor.

Mutation

A change in the DNA sequence.

RNA

Has uracil (U) instead of thymine (T).

Protein Synthesis

Includes transcription and translation.

Gene Expression

Can be affected by the environment (e.g., Himalayan rabbit).

Selective Breeding

Produces organisms with desired traits.

Genetic Engineering

Alters an organism's DNA.

Restriction Enzymes

Cut DNA at specific sequences.

Plasmid

A small circular DNA found in bacteria.

Recombinant DNA

Made by combining DNA from different organisms.

Species

Can reproduce and create fertile offspring.

DNA Fingerprinting

Identifies individuals using DNA patterns.

Stem Cells

Undifferentiated and can become any type of cell.

Evolution

The process by which organisms change over time.

Natural Selection

Survival of the fittest—best adapted survive and reproduce.

Variation

In a population, caused by mutations.

Population

All members of one species in an area.

Community

All populations in an area.

Competition

The struggle for limited resources.

Limiting Factors

Control population size (e.g., food, water, space).

Carrying Capacity

The maximum number of individuals an area can support.

Predators

Eat other organisms (prey).

Niche

The role a species plays in its ecosystem.

Autotrophs

Producers that make their own food using photosynthesis.

Heterotrophs

Consumers that must ingest food.

Herbivores

Eat plants; carnivores eat meat.

Decomposers

Break down dead organisms; scavengers eat already-dead animals.

Parasites

Live on or in a host and cause harm.

Food Chain

Simple, showing one path of energy.

Food Web

Complex, showing many connections.

Energy Source

The main energy source for Earth is the Sun.

Energy Pyramid

The most energy is at the bottom.

Energy Transfer

Only 10% of energy is passed to the next level; the rest is lost as heat.

Biodiversity

More biodiversity leads to more stability in an ecosystem.

Keystone Species

One that many others depend on.

Interdependency

When species rely on each other to survive.

Ecological Succession

The gradual change to a stable climax community.