7th Grade Core Science Vocabulary
1
absolute age
The age of a rock given as the number of years since the rock formed.
Example: Scientists use radioactive dating to determine the absolute age of rocks.
(Earth’s History: Ch. 8, p.272)
2
active transport
The movement of materials through a cell membrane which requires energy.
3
alleles
The different forms of a gene some of which are dominant and some are
recessive. An organism’s traits are determined by the alleles it inherits from
its parents.
(Cell Biology: Ch. 3, p.106)
A dominant allele is one whose trait always shows up in the organism when
the allele is present.
The trait expressed by a recessive allele is hidden whenever a dominant
allele is present. (Genetics: Ch.5, p.157)
4
asexual
reproduction
A reproductive process that involves only one parent and produces offspring
identical to the parent.
Example: Bacteria reproduce by a form of asexual reproduction called binary
fission, in which one cell divides to form two identical cells. Most singlecelled organisms reproduce this way.
5
cell cycle
The regular sequence of growth and division that cells undergo.
During the cell cycle a cell grows, prepares for division, and divides into two
new “daughter” cells undergoing interphase, mitosis and cytokinesis.
(Genetics, Structure & Function: Ch. 9, p.328)
(Cell Biology: Ch 4, p.130)
6
cellular
respiration
The process by which cells break down simple food molecules such as
glucose to release the energy they contain.
Example: sugar + oxygen  carbon dioxide + water + energy
(Cell Biology: Ch 4, p124)
7
chromosomes
A double rod of condensed chromatin formed in mitosis during prophase.
Chromatins are the threadlike strands of genetic material found in the
nucleus. Each chromosome has two rods called chromatids held together by
a centromere.
(Cell Biology: Ch 4, p 131)
8
cornea
A transparent tissue that covers the front of the human eye.
Example: Light first enters the eye through the front surface called the cornea.
(Structure & Function, Physical Principles: Ch. 15, pp.63, 615)
9
concave lens
A lens that is thinner in the center than at the edges.
Example: Light rays entering a concave lens diverge.
(Physical Principles: Ch. 2, p.60)
10
convex lens
A lens that is thicker in the center than at the edges. Convex lenses are
used in microscopes to magnify the image of the specimen.
Example: Light rays entering a convex lens converge.
(Light: Ch. 2, p. 59)
11
diffusion
The process by which molecules move from an area of higher
concentration to an area of lower concentration. Cells move materials into
and out of the cell membrane by diffusion.
Example: Air freshener sprayed in one corner of a room can eventually be
smelled in the entire room as the molecules of freshener move from an area of
high concentration to an area of lower concentration by diffusion.
(Cell Biology: Ch. 3, p. 103-104)
12
DNA
Deoxyribonucleic acid found in the chromatin in the nucleus; the genetic
material that carries information about an organism and is passed from
parent to offspring. The information in DNA is used to direct all of the cell’s
functions.
(Cell Biology: Ch. 3, p.101)
13
electromagnetic The complete range of electromagnetic waves that originate from the sun,
spectrum
placed in order of increasing frequency, ranging from radio waves which
have the lowest frequency to gamma rays with the highest frequency.
14
Enzyme
(Physical Principles: Ch. 2, p.43)
A protein that speeds up chemical reactions in a living thing.
(Cell Biology: Ch. 3, p. 100)
15
eukaryote
An organism whose cells contain nuclei.
(Evolution: Ch 7, p 254)
16
evolution
The gradual change in a species over time.
17
function
A process that enables an organism to survive.
(Evolution: Ch 7, p 228)
Example: The function of the heart is to pump blood throughout the body.
(Structure & Function in Living Structures, Ch. 1, p. 16
18
genes
The set of information that controls a trait; a segment of DNA on a
chromosome that codes for a specific trait.
19
genotype
An organism’s genetic makeup or allele combinations. The DNA code of the
organism. (Genetics: Ch 5, p 166)
20
half-life
The time it takes for half of the atoms in a radioactive element to decay. Into
(Genetics:Ch.5, p157)
a different element.
(Earth’s History: Ch. 8, p. 280)
Example: The half-life of a radioactive element is the amount of time it
takes for half of the radioactive atoms to decay.
The half-life of potassium-40 is 1.3 billion years.
21
heredity
The passing of physical characteristics from parents to offspring.
(Genetics: Ch 5, p.154)
22
heterozygous
Having two different alleles for a trait. In a heterozygous organism the
dominant trait will mask a recessive trait. If A represents an allele for tall
stems, and a represents an allele for short stems, then a heterozygous gene
such as Aa will always have tall stems.
(Genetics: Ch 5, p.166)
23
homeostasis
The maintenance of stable internal conditions in an organism.
Example: Your body maintains a temperature of about 37o C. When you get hot,
your body responds by sweating to cool you down. When you get cold, your
muscles twitch and cause you to shiver in an attempt to generate heat.
( Structure & Function, Ch. 13, p. 516)
24
homozygous
Having two identical alleles for a trait.
Example: If A represents the dominant allele for tall stems and a represents
the recessive allele for short stems then AA is homozygous dominant and
always has tall stems, while aa is homozygous recessive and always has
short stems.
(Genetics: Ch 5, p.166)
25
hybrid
An organism that has two different alleles for a trait; an organism that is
heterozygous for a particular trait.
(Genetics: Ch 5, p.158)
26
mitosis
The stage of a cell’s life cycle during which the cell’s nucleus divides into two
nuclei with identical DNA. The phases of mitosis are prophase, metaphase,
anaphase and telophase.
(Cell Biology: Ch 4, p 130) (Insert picture of cells at each stage of mitosis)
27
mutation
A change in a gene or chromosome. A mutation can be an addition, a
substitution or a deletion along the genetic code.
(Genetics: Ch 5, p.80)
28
natural
selection
The processes by which individuals are better adapted to their environment
are more likely to survive and reproduce than others of the same species.
The Theory of Natural Selection was proposed by Charles Darwin in 1859.
29
neuron
A cell that carries information through the nervous system. A neuron has a
large cell body that contains the nucleus, threadlike extensions called
dendrites, and an axon.
(Evolution: Ch 7, p. 229)
(Structure & Function: Ch. 15, p.602)
30
opaque
Reflecting or absorbing all of the light that strikes it.
(Physical Principles: Ch. 2, p.47)
31
osmosis
The diffusion of water molecules through a selectively permeable membrane.
Example: Plant roots are able to draw water from the soil because of osmosis.
(Cell Biology: Ch. 3, p. 104-105)
32
passive
transport
The movement of materials through a cell membrane without using a cell’s
energy.
(Cell Biology: Ch. 3, p. 106)
33
phenotype
An organism’s physical appearance or visible traits. The way an organism
looks.
(Genetics: Ch 5, p.166)
34
placenta
In most mammals, it is the membrane that becomes the link between the
developing embryo or fetus and the mother. The placenta supplies food and
oxygen from the mother’s blood to the growing embryo. The placenta also
removes wastes from the embryo and transports them to the mother’s blood
for her to excrete.
(Structure & Function, Ch. 12, pp. 491, 659)
35
prokaryote
An organism whose cells lack a nucleus and some other cell structures.
Example: Bacterial cells are prokaryotes while plant and animal cells are
eukaryotes.
(Evolution: Ch 7, p 253)
36
Punnett Square
A chart that shows all the possible combinations of alleles that can result
from a genetic cross.
(Genetics: Ch 5, p 164)
37
38
radioactive
decay
reflection
The breakdown of a radioactive element, releasing particles and energy.
(Earth’s History: Ch. 8, p.280)
The bouncing back of an object or wave when it hits a surface through which
it cannot pass.
(Physical Principles: Ch. 2, p. 53)
39
refraction
The bending of waves as they enter a new medium at an angle.
(Physical Principles: Ch. 2, p. 57)
40
relative age
The age of a specific rock or fossil compared to the ages of rock layers that it
is found near.
(Earth’s History: Ch. 8, p. 272)
41
retina
A sheet of light-sensitive cells at the back of the eye on which an image is
focused.
42
ribosome
A small grain-like structure responsible for the production of protein in the
cell. Can be found either floating in the cytoplasm or attached to the
endoplasmic reticulum.
(Structure & Function, Physical Principles, Ch. 15, pp. 48, 616)
(Cell Biology: Ch. 3, p. 93)
43
sexual
reproduction
A reproductive process that involves two parents that combine their genetic
material to produce a new organism, which differs from both parents.
(Genetics, Ch. 5 & 9, pp. 170, 328)
44
structure
45
synapse
The way an organism is put together as a whole. A structure is any
identifiable part of an organism.
Example: Animal eyes come in many shapes and sizes. Although each
animal might see things differently, all of their eyes have a similar function
and operate on similar physical principles.
(Investigation & Experimentation Ch. 1 p. 16)
The junction where one neuron can transfer an impulse to another structure.
Example: When a nerve impulse reaches the tip of axon, chemicals are
released into the gap at the synapse. The chemicals carry the nerve impulse
across the gap.
( Structure & Function, Ch. 15, p.604)
46
translucent
That which scatters light as it passes through.
(Physical Principles: Ch. 2, p.47)
Example: Smoke, fog and clouds scatter light as it passes through the air.
Waxed paper and frosted glass are examples of translucent materials.
Details are usually blurred when seen through translucent materials.
47
transparent
48
zygote
That which transmits light without scattering it.
(Using Physical Principles: Ch. 2, p.47)
A fertilized egg, produced by the joining of a sperm and an egg.
(Genetics, Structure & Function, Ch. 10, p. 365)