Living Environment

cell

the basic unit of structure and function that makes up all organisms

metabolism

all the chemical reactions that occur within the cells of an organism

homeostasis

the ability of an organism to maintain a stable internal environment even when the external environment changes

reproduction

the process by which organisms produce new organisms of the same type

cell respiration

the process in which nutrients are broken apart, releasing the chemical energy stored in them

synthesis

a life process that involves combining simple substances into more complex substances

organic

term used to describe molecules that contain both hydrogen and carbon

inorganic

a type of molecule that does not contain both carbon and hydrogen but can contain any other combination of elements

organelle

a structure within the cell that carries out a specific functiontissues

tissues

a group of specialized cells that perform a specific function

organ

a body structure made of different kinds of tissues combined to perform a specific function

organ system

several organs that work together to perform a major function in the body

cytoplasm

the jellylike substance that is between the cell membrane and the nucleus and that contains specialized structures

nucleus

a large structure within a cell that controls the cell’s metabolism and stores genetic information, including chromosomes and DNA

vacuoles

storage sacs within the cytoplasm of a cell that may contain either wastes or useful materials, such as water or food

ribosomes

tiny structures in the cell that are the sites of protein production

mitochondria

pod-shaped organelles that contain enzymes used to extract energy from nutrients

enzymes

proteins that speed up the rate of chemical reactions in living things

chloroplasts

green organelles that contain chlorophyll; where photosynthesis takes place

cell membrane

the thin boundary between the cell and its environment

diffusion

the movement of molecules from areas of high concentration to areas of low concentration

active transport

the process by which cells use energy to transport molecules through the cell membrane from areas of low concentration to areas of high concentration

digestion

the process that breaks down large food molecules into simpler molecules that the organism can use

amino acids

any one of several building blocks of protein

simple sugars

the result of digested starches

receptor molecules

certain protein molecules in the cell membrane that can receive chemical messages from other cells

hormones

a chemical produced in the endocrine glands

respiration

the process by which the chemical bond energy stored in nutrients is released for use in cells

circulation

the flow of materials within a cell as well as between parts of a multicellular organism

excretion

the removal of all the wastes produced by the cells of the body

immunity

the body’s ability to destroy pathogens before they cause disease

enzymes

proteins that speed up the rate of chemical reactions in living things

respiration

the process by which the chemical bond energy stored in nutrients is released for use in cells

synthesis

a life process that involves combining simple substances into more complex substances

biochemical process

a chemical process that occurs in a living thing

photosynthesis

the process by which some organisms are able to capture light energy and use it to make food from carbon dioxide and water

homeostasis

the ability of an organism to maintain a stable internal environment even when the external environment changes

glucose

a sugar that is a major source of energy for cells

ATP

(adenine triphosphate) a compound that stores energy in cells

chloroplasts

green organelles that contain chlorophyll; where photosynthesis takes place

gas exchange

the process of obtaining oxygen from the environment and releasing carbon dioxide

catalyst

a substance that can speed up the rate of a chemical reaction without being changed or used up during the reaction

pH

a measure of whether a substance is acidic, neutral, or basic

dynamic equilibrium

the constant small corrections that normally occur to keep an organism’s internal environment within the limits needed for survival

feedback mechanism

a cycle in which the output of a system either modifies or reinforces the first action taken by the system

stimulus

any change in the environment that causes an organism to react

pancreas

an endocrine organ that secretes insulin

insulin

a hormone that prompts glucose to move from the blood into body cells, resulting in a lower glucose level in the blood

guard cells

specialized cells that control the opening and closing of the pores on the surface of a leaf

disease

a condition, other than injury, that prevents the body from working as it should

pathogen

an organism that invades the body, causing disease

virus

a nonliving particle of protein and genetic material that reproduces by invading the cell of a living organism

bacterium

any one of many single-celled organisms without a distinct nucleus

fungi

the kingdom of organisms that are mostly multicellular, have cell walls made of chitin, and are heterotrophic

parasite

an organism that survives by living and feeding on other organisms

immune system

the body’s primary defense against disease-causing pathogens

antigen

a molecule found on the outer surfaces of cells that the immune system recognizes as either part of the body or an outside invader

antibody

a protein, produced by the immune system, that either attacks invading pathogens or marks them for killing

microbe

any microscopic organism

vaccines

a substance made of weakened, killed, or partial pathogens and designed to protect the body from future invasions of that pathogen

AIDS

(acquired immunodeficiency syndrome) the disease that results when the HIV virus attacks the human immune system

allergy

a condition in which a person’s immune system is overly sensitive to environmental substances that are normally harmless

gene

a segment of DNA (on a chromosome) that contains the code for a specific trait

trait

a characteristic that is passed from parent to offspring through the genes

heredity

the passing of traits from parent to offspring

DNA

(deoxyribonucleic acid) the material found in all cells that contains genetic information about that organism

chromosome

a thick threadlike structure that contains genetic information in the form of DNA

asexual reproduction

a method of reproduction in which all the genes passed on to the offspring come from a single individual or parent

sexual reproduction

a method of reproduction that involves two parents producing offspring that are genetically different from either parent

clone

an organism that is genetically identical to the organism from which it was produced

sperm

the male sex cell

egg

a sex cell produced by a female

genetic recombination

the formation of a new combination of genes during sexual reproduction

subunit

the section of a DNA molecule that contains a sugar, a phosphate, and a base

bond

a chemical link between atoms that hold molecules together

replicate

to copy

template

the pattern for a new molecule

mutation

any alteration in the sequence of DNA

expressed

the way that an unseen gene is seen in an organism as an actual physical trait

genetic engineering

a set of technologies that humans use to alter the genetic instructions of an organism by substituting DNA molecules

biotechnology

the combination of technology and biological sciences

selective breeding

the process of choosing a few organisms with desirable traits to serve as the parents of the next generation

asexual reproduction

a method of reproduction in which all the genes passed on to the offspring come from a single individual or parent

sexual reproduction

a method of reproduction that involves two parents producing offspring that are genetically different from either parent

sperm

the male sex cell

egg

a sex cell produced by a female

species

A group of organisms that share certain characteristics and can mate with one another, producing fertile offspring

sex cell

an egg (female) or a sperm (male)

gametes

an egg or sperm cell; a sex cell

mitosis

the process that divides the cell’s nucleus into two, each with a complete set of genetic material from the parent cell

meiosis

the process that results in the production of sex cells (sperm and egg)

fertilization

the process that combines a sperm cell and an egg cell

zygote

the cell that results from the joining of the egg and sperm

recombination

the additional mixing of genetic material from a sperm and egg which results in a unique combination of genes

differentiation

the process that transforms developing cells into specialized cells with different structures and functions

embryo

an organism in the early stages of development

gene expression

the result of activated genes

ovary

the organ of the human female reproductive system that produces an egg cell, the female gamete

progesterone

a hormone associated with sexual development and the reproductive system

estrogen

a hormone (produced by the ovaries) that controls female sexual development and the reproductive process