Transcript Grade 8 Review For Exam

Grade 8 Review For Exam
June 2016
The Living World
Diversity of Life Forms
Adaptations
• Anything that helps an organism survive in its
environment is an adaptation.
• It also refers to the ability of living things to
adjust to different conditions within their
environments.
Structural/Physical Adaptations
• A structural adaptation (or physical) involves
some part of an animal's body, such as the size or
shape of the teeth, the animal's body covering, or
the way the animal moves.
• Examples of structural adaptations:
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How they move
Protective coloration (camouflage)
Mimicry
What & how they eat
How they reproduce
Physical Adaptations of the Beaver:
• The body of the beaver is adapted to aquatic
life. It has:
– A broad, flat tail
– Thick oily fur
– Webbed hind feet
– It has long front teeth
(incisors) to cut down
trees & feed on leaves & bark.
Behavioral Adaptations
• Behavior adaptations include activities that help an animal
survive.
• Behavior adaptations can be learned or instinctive (a
behavior an animal is born with).
• Social behavior - some animals live by themselves, while
others live in groups.
• Behavior for protection - An animal's behavior sometimes
helps to protect the animal. Ex: the opossum plays dead. A
rabbit freezes when it thinks it has been seen.
• Other examples:
– Migration
– Hibernation
– How they communicate
Genes & Chromosomes
• Chromosomes are found in the nucleus of
eukaryotic cells.
• Chromosomes contain all the genes required
to produce an individual.
• Genes are small segments with specific
locations on the chromosomes. They
determine the unique characteristics of a
species.
Diffusion
• Is the tendency of molecules to spread out from areas
of high concentration to areas of low concentration.
• Is a passive process ( energy input is not needed)
• It occurs because the kinetic energy of molecules
drives them to move randomly & collide with other
molecules or the sides of their container, eventually
resulting in the net movement from an area of high
concentration to an area of lower concentration.
• The molecules tend to become uniformly distributed.
Contin. of diffusion”
• It accounts for many processes in the body,
including:
– Movement of gases in the lungs & blood stream
– Passage of nutrients in the digestive tract
– Absorption of fluids in the excretory system
The Rate of Diffusion
• depends on:
– Temperature: At higher temperatures, molecules
have more energy, travel faster, collide more often, &
diffuse faster.
– Size of particles: Larger molecules have a greater
chance of collision than smaller ones. Smaller
molecules move more rapidly & farther when
bumped.
– Concentration gradient (difference in concentration
between two solutions): When the gradient is high,
diffusion occurs rapidly. As the concentration evens
out, the rate of diffusion decreases.
Osmosis
• Is the movement of water molecules through a selectively
or semi-permeable membrane (a membrane that controls
what passes through its pores).
• It is a special case of diffusion and is important because
most substances in the body are dissolved in water (and
about 70% of a cell is water).
• Often the size of the pores in a membrane controls the
passage of molecules.
– If pores are small, only small molecules get through.
• It is a passive process (does not require an input of energy).
The energy of motion of the molecules is sufficient to move
them across the membrane.
Osmosis
Solute in Water
Two Vital Functions of Cells
• 1. Photosynthesis:
= A chemical reaction carried out by plants in their
chloroplasts in which they make sugars called
carbohydrates from water, carbon dioxide and
sunlight.
Inputs
Outputs
Sunlight
Sunlight
• 2. Cellular respiration:
= a chemical reaction in which the energy contained
in food is released. i.e., it transforms
carbohydrates (sugar) into energy.
-it is performed by the mitochondria.
Inputs
Outputs
Oxygen + glucose (sugar) ― > CO2 + Water + Energy
• Photosynthesis and cellular respiration are
OPPOSITE reactions!
• CO2 + Water + Solar energy  Glucose + O2
• Glucose + O2  CO2 + Water + Energy
Survival Of Species
Reproduction Organs
• Refer to diagrams attached to back of review
package.
Male Reproductive Organs
Male Reproductive Organs
Reproductive organ
Purpose
Scrotum
Pouch that contains the testicles. Holds testicles away from
body because sperm production requires temperatures
below body temperature.
Testicles
Contain the seminiferous tubules.
Seminiferous tubules
Produce an average of 400 million male gametes per day.
Epididymis
The sperm produced are stored in this small, elongated
organ lying above the testicles.
Vas deferens
The sperm enter the vas deferens before being released
outside the body during ejaculation.
Prostrate & seminal
vesicles
They produce semen, the fluid that contains sperm. Semen
helps the sperm move & is rich in sugar to provide energy
for swimming into the woman’s vagina after ejaculation.
Male Reproductive Organs
Reproductive organ
Purpose
Urethra
Semen flows through this tube during ejaculation. Urethra
also carries urine from the bladder outside the body.
Cowper’s gland
Cowper’s gland releases a fluid into the urethra, which
neutralizes the acidity caused by any remaining traces of
urine that could threaten the survival of sperm.
Female Reproductive Organs
Follicles inside
Female Reproductive Organs
Reproductive Organ
Purpose
Ovaries
A woman has 2 ovaries. They take turns releasing 1 ovum
every 28 days. This is called ovulation.
Follicles
They are located in the ovaries. Each follicle contains a single
ovum & brings it to full maturity.
Fallopian Tubes
The ovum released by the follicle travels through the
fallopian tube to reach the uterus. An ovum survives
between 24-48 hours in the fallopian tube, where it can be
fertilized.
Uterus
A hollow, pear-shaped organ where the zygote develops if
the ovum is fertilized by a sperm.
Vagina
The passage into which the penis penetrates to release its
sperm. The baby also leaves the uterus through the vagina
during birth.
Gametes
• Are necessary for sexual reproduction (Most
vertebrates reproduce this way).
• Male animals produce male gametes or
spermatozoa.
• Female animals produce female gametes or ova.
• Spermatozoa & ova each contain half the genetic
material (n) of the future offspring.
• When they unite, the future offspring contains
the full amount of genetic material (2n).
Cycle of Sexual Reproduction in
Animals
Fertilization of Gametes
• Occurs when a spermatozoon & ovum of a
single species combine.
• Must take place in a moist environment so
that sperm can move, & egg membrane is
supple enough for sperm to penetrate (the
cells will die if they dry out).
Sexual Reproduction & Gametes
• To be successful, the following criteria must be
met:
– Male & female gametes must be at the same
place at the same time.
– The zygote must obtain nutrients & protection to
survive, get warmth & moisture needed for its
development.
Contraception
• If a female does not have a monthly cycle in
which the lining of her uterus thickens & she
releases an egg, she cannot get pregnant. This
is controlled by her hormones.
• A female’s monthly menstrual cycle can be
controlled by hormonal birth control – such as
the pill, the patch, the ring or injections
(Depo-Provera).
Contraception
• Other methods create a physical barrier to
block the sperm from getting to an egg, such
as the male or female condom, or an
intrauterine device (IUD).
• Some methods aim to kill the sperm with
spermicides, such as the sponge (soaked in
spermicide) & spermicide gels.
Contraception
• Still other methods include:
– Surgery (vasectomy or tubal ligation)
– Natural or rhythm method
– Abstinence – the only one that is 100% effective!
Sexually Transmitted Diseases
• Are either bacterial (can be cured with
antibiotics) or viral (no specific cure, we only
treat the symptoms).
• Common bacterial ones: Chlamydia (the most
common STI in young people) & Gonorrhea,
Syphilis
• Common viral ones: Herpes, HPV, HIV/AIDS,
Hepatitis B & C
• Refer to PowerPoint on website for details.
Behaviors That Might Lead to STIs
• Unprotected sex (not wearing a condom)
• Multiple sexual partners
• Using drugs and alcohol because it clouds your
judgement
• Believing that it won’t happen to you (magical
thinking)
• Not asking your potential partner to get tested
(& not getting tested yourself)
Mass
• Is a measure of the amount of matter in a
substance.
• To measure it we use a scale – usually a digital
scale or a triple beam balance scale.
• The unit of measure is the gram (g) or
kilogram (kg).
Volume
• Is a measure of the amount of space an object
occupies.
• To measure it we can use a ruler (if it has a
regular shape, Ex: a cube = L x W x Ht), or a
graduated cylinder (if it is a liquid, or is a solid
with an irregular shape, Ex: a bumpy rock).
• The unit of measurement is the cubic centimeter
(cm3) (if you used a ruler) or the Litre (L) or
mililitre (mL) (if you used a graduated cylinder).
Temperature
• A measure of the intensity of heat emitted by
an object or substance.
• It provides an indication of the average speed
of motion of the particles in the substance.
– It is a impossible to directly measure the speed of
particles in matter because they are too small &
too quick.
• We measure temperature with a thermometer
• The unit of measure is the degree Celcius (0C).
States of Matter
• Matter occurs in three states:
1. Solid
2. Liquid
3. Gas
• A change in temperature will cause a
substance to change state.
Acidity Vs. Alkalinity
• Acids and bases are 2 groups of important
chemicals with the following characteristics:
Acids
Bases
Sour
Bitter
No distinct feel
Slippery
Turn blue litmus red
Turn red litmus blue
pH < 7
pH > 7
Acids Vs. Bases
Characteristic Vs. Non-Characteristic
• Characteristic properties are so specific that
they help you identify a substance. They are
often unique to that substance.
– Ex: density, melting point, boiling point
• Non-characteristic properties are general and
do not help you identify a substance.
– Ex: color, shape, mass, volume, texture
What are Mixtures?
• The atoms & molecules sometimes combine
without undergoing a chemical reaction.
Instead, they form a mixture.
• A mixture is made up of at least 2 different
substances which can always be isolated using
physical separation techniques (no chemical
bonds broken).
• Solutions are an important type of mixture.
Ex: Air, tap water, steel
• A solution is a liquid homogeneous mixture
containing dissolved substances. Cannot be
separated by filtering, but can by boiling.
• Homogeneous = component substances
cannot be distinguished, even with the aid of
a magnifying instrument.
• In contrast, a heterogeneous mixture would
be one in which the individual components
can be distinguished.
Separation of Mixtures
There are several ways to separate mixtures:
• Physical removal – pick parts out with fingers
or tweezers. Ex: In a salad, pick out the
onions.
• Use a magnet. Ex: Separating iron from sand.
How it works: The magnet sticks to the iron
but not to the sand.
• Filtering (filtration) -used to separate a solid
(or suspension) from a liquid. How it works:
The liquid (& anything dissolved in the liquid)
passes through holes in the filter paper but
the solid particles are too big and get stuck.
– Example: Separating dirt from salty water.
• Evaporation can be used to separate a
dissolved SOLUTE (the substance dissolved)
from a SOLUTION.
– Ex: Evaporate water off a salt water solution.
• Distillation = boiling, collecting the steam &
condensing it. Ex: to purify alcohol
• Sedimentation = particles in suspension in a
fluid will tend to settle on a surface if the
suspension is left, undisturbed.
– Ex: Used in water filtration plants to get rid of grit
in water.
Physical Changes
• Alters neither nature nor characteristic
properties of matter. The atoms and
molecules of the substance do not change.
Chemical Changes
• Alter the nature & characteristic properties of
matter. The bonds between atoms are
rearranged.
Signs of a Chemical Change
1) Change in color (not a change in shade as
light red to dark red, but a total change in
color as red to blue)
2) You see bubbles of gas – it fizzes
3) A solution turns cloudy & a solid falls to the
bottom (precipitate forms)
4) Heat or light is given off or taken in (i.e.,
something gets hot or cold)
5) Electricity is produced (i.e., in a battery)
Chemical Changes
-You usually cannot reverse a chemical change.
Ex: you cannot “unburn” paper
-Alter the number of electrons in an atom
Earth & Space
General Characteristics of the
Lithosphere
• The lithosphere is the rigid structure that
comprises the Earth’s crust & part of the
upper mantle.
• It ranges in thickness from 70 km 0Beneath
oceans) to 150 km (beneath continents).
Lithosphere
• It is essential to life:
– It allows plants to send down roots to anchor
themselves & provides them with minerals they
need to grow & develop
– It offers habitats to animals
– It holds natural resources for humans, including oil
& natural gas, rocks & minerals
– It gives us the materials we need to build things
on which our well-being depends
Lithosphere
• It is constantly evolving due to the influence of
several factors such as climate & human
activity.
Rocks From The Lithosphere
• Rocks are heterogeneous solids composed of
many minerals (minerals have well defined
properties whereas rocks have physical and
chemical properties that are not strictly defined)
• Rocks are formed by different processes:
– Rocks that are formed by water pressure are called
sedimentary
– Rocks that are formed by volcanic activity are called
igneous
– Metamorphic rock are rocks that have been
transformed by high temperatures & pressure.
Renewable & Non-renewable Energy
Resources
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Hydro energy - R
Wind energy - R
Solar energy - R
Geothermal energy - R
Nuclear energy - NR
Fossil fuel energy - NR
Biomass & biofuels - NR
Battery & hydrogen energy - NR
Eclipses
Solar eclipse: an eclipse in which the sun is
obscured by the moon.
Lunar eclipse: an eclipse in which the moon
appears darkened as it passes into the earth's
shadow.
Solar Eclipses
Lunar Eclipses
Seasons
• Seasons happen because the Earth's axis is
tilted at an angle of about 23.4 degrees in
relation to its path around the Sun.
• Because of this axial tilt, different parts of the
Earth point toward or away from the Sun at
different times of the year.
Seasons
• Around the June solstice, the North Pole is
tilted toward the Sun and the Northern
Hemisphere gets more of the Sun's direct rays.
This is why June, July and August are summer
months in the Northern Hemisphere.
Seasons
• At the same time, the Southern Hemisphere
points away from the Sun. So, people there
have winter during the months of June, July
and August. Summer in the Southern
Hemisphere happens in December, January,
and February, when the South Pole is tilted
toward the Sun and the Northern Hemisphere
is tilted away.
The Technological World:
Mechanical Engineering
Types of Energy
• Review in your notes the various types of energy:
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Potential
Elastic
Kinetic
Radiant
Electrical
Magnetic
Thermal
Chemical
Nuclear
Accoustic
Basic Mechanical Functions
• Links & guiding controls
Guiding Controls
• 3. Helical guiding – ensures the translational motion
of a part while it rotates around the same axis.