Download 2009 8th Grade Science Study Guide Answers

Chapter 1 Semester Exam Study Guide Answers/8th Grade Science
1. Compare = they both are observed repeatedly; they both involve patterns; and
both are scientific
Contrast = a scientific theory explains a pattern in the natural world; a scientific
law describes a pattern in the natural world
2. 3 branches of science = Life, Earth, and Physical
Compare = all three relates to science
Contrast = Life science is the study of living things and the ways in which they
interact; Earth science is the study of Earth systems and the systems in space;
Physical science is the study of matter and energy.
3. An inference is when one makes a conclusion based on an observation. An
observation is when one looks at, observes, or simply watches something.
4. order = state the problem, research problem, form a hypothesis, test hypothesis
(experiment), analyze data, draw a conclusion, repeat the process, communicate
results – The scientific method is important because it allows one to solve
problems, understand nature, communicate findings, etc.
5. A constant is a variable in an experiment that remains the same. A variable is a
factor that can be changed in an experiment.
7. The variable that is changed in an experiment is the independent variable. The
dependent variable changes as a result of the independent variable. The dependent
variable is usually the one observed in an experiment.
6. A controlled experiment involves changing one factor and observing its effect
on another while keeping all other factors constant.
8/1. (EXAMPLE ONE): independent variable = standard diet or supplemented diet
(with blueberries, strawberry, or spinach powder);
8/2.dependent variable = memory tests and motor skills test
8/3. The hypothesis is that antioxidants found in blueberries may slow down the
process of aging.
9. Quantitative Data – data consisting of numbers. Example: The flight time of a
paper airplane. Qualitative Data – data consisting of verbal descriptions or
information gathered using scales without numbers. Example: The wing shape
(wide/narrow)
10. Objective observation is an observation based on fact. Ex. My paper airplane is
made out of white paper. Subjective observation is an observation based on
opinion. Ex. My paper airplane design is the best.
11. It is important to always use the proper safety equipment to avoid accidents in
the lab and in the field.
Chapter’s 3 and 5
12. Barred Spiral, spiral, elliptical, and irregular galaxies:
1. Barred Spiral Galaxy:
* A galaxy with a bar of stars and interstellar matter, such as dust and gas, across its
center.
2. Spiral Galaxy:
* A spiral-shaped system of stars, dust, gas, and clouds.
* Has a spherical central bulge of older stars surrounded by a flattened galactic disk
that contains a spiral pattern of young, hot stars as well as interstellar matter.
3. Elliptical Galaxy:
* A galaxy that appears spherical or foot-ball shaped.
* Comprise mostly of old stars and contain very little dust and gas that can form
stars.
4. Irregular Galaxy:
* Appears disorganized or disordered, without a distinct shape.
* Usually rich in interstellar matter, such as gas and dust particles.
13. Most astronomers think that the Milky Way Galaxy is most likely a barred
spiral galaxy. They contain more than one hundred
billion stars and has a diameter of about 100, 000 light years.
14.
It takes 29.5 days for the Moon to complete its cycle of phases. As noted the moon
reaches a major phase every seven days after the new moon. The first of which is the first
quarter moon occurring after 7.4 days. Between the new and first quarter is the time of
the waxing crescent moon. 14.8 days into trip around the earth we see a full moon, but
not before the waxing gibbous make an appearance. After the full moon a state of waning
begins on the 15th day. Along with a last quarter moon both a waning gibbous and
crescent moon is visible before a new moon cycle starts a new on the 29th day.
15. The tilt of the Earth’s axis and the Earth’s revolution around the sun on its axis are
what causes the changing in seasons on the Earth.
16.
Lunar Eclipse p. 84
17.
Solar Eclipse p. 83
18. A light year is the amount of time it takes for light to travel in one year. The
purpose of light years is to measure distances in space.
19. The Doppler Shift occurs with light as well as with sound. The Doppler Shift
causes changes in the light coming from distant stars and galaxies. If a star is moving
toward Earth, the dark lines that make up the spectrograph will move toward the blueviolet end of the spectrum. If a star is moving away from Earth, the dark lines that make
up the spectrograph will move toward the red end of the spectrum.
20. A spectrometer is used by astronomers to analyze stars. They can determine
what stars are made of even if the stars are very far away because stars radiate light.
21. Absolute magnitude is the measure of how bright a star really is, if all stars
were the same distance from Earth. Star magnitude is indicated by a number. A lower
number means a brighter star. A higher number means a dimmer star.
22. The purpose of nuclear fusion in the core of a star is to generate energy,
radiate light, or to produce heat.
23. The reason that the moon has its different phases is because of the Moon’s
revolution around the Earth.
24. Light years are units of length to measure the distance from Earth to stars
other than the Sun.
Chapter 11
25. A gene is a unit found on a cell’s chromosomes that carries information about a trait
of the organism. Chromosomes are located inside cells, genes are located on
chromosomes and DNA is located inside genes. Analogy: Gene: Chromosome; Bone:
Skeleton
26. DNA is a molecule that carries genetic information. It is located inside of genes.
DNA: Genes; Chapter: Book
27. 39
28. Spiral staircase
29. & 31.
Cell Division and Sex Cell Formation in Humans
Cell Division & Production Cell Division & Sex Cell
of Body Cells
Formation
Process used
Mitosis
Meiosis
DNA duplicated?
yes
Yes
Nucleus Divides
Yes/once
Yes/twice
Number of cells formed
2 (same genetic
4(different genetic
information)
information)
Chromosome Number of
46
46
beginning cell
Chromosomes in each new
46
23
cell
30. Interphase, prophase, metaphase, anaphase, telophase, and cytokinesis
32.
A type of
reproduction
How many parents?
Genetic material of
offspring’s
Process involved
Types
33.
Differences in Sexual & Asexual Reproduction
Sexual
Asexual Reproduction
yes
Yes
2
Different from parents
1
Same as parent
meiosis
Mitosis
Binary fission, budding,
regeneration, and cloning
Fig. 1/ A picture of a hydra reproducing by asexual
reproduction. Budding is a type of asexual reproduction that involves a bud
growing on the body of an organism and becoming the exact replica of the
original organism. Mitosis helps this bud to grow become it involves the
growth of organisms.
34. Fertilization is the coming together of the egg and sperm in which each egg and
sperm contains 23 chromosomes each. When they join, they will produce a zygote having
46 chromosomes in 23 pairs.
35. Part A: Parents alleles: Gg x gg
G
g
Gg
g
Gg
Genotypes = Gg/2/4=50%; gg/2/4=50%
Part B: Parents alleles: Gg x Gg
G
GG
Gg
G
g
Genotypes =
GG = ¼=25%
Gg = 2/4=50%
gg=1/4=25%
g
gg
gg
g
Gg
gg
Phenotypes
Square Pants = ¾=75%
Round Pants = ¼= 25%
36 – 38. Students must refer to their apparatus sheets to draw, label, and describe each
use.
39. homozygous recessive = having two of the same alleles but in recessive forms
(example: aa); homozygous dominant = having two of the same alleles but both are
dominant alleles (example AA); heterozygous = having different alleles for a trait
(example Aa)
40. Desirable traits can be cultivated with greater frequency in the purebred population
than in the general population.
41. BB x bb
b
b
B
Bb
B
Bb
Bb Bb
Phenotype: 4 brown eyes = 4/4 = 100%
Genotype: 4 Bb or 100%; Bb or 4/4 Bbs