~ ANSWER KEY ~ASK 8 Science

6th Grade Reviewaka: Everything You Learned in 6th Grade and a Few Things You Forgot…

ECOLOGY: the Study of the Interrelationships and Interactions Among Organisms and their Environment

Key Concept: Everything is connected!!Key Terms: Ecosystem, Producer, Consumer, Decomposer, Food Chain, Food Web, Niche, Habitat, Species, Population, Community, Photosynthesis, Respiration, Water Cycle aka Hydrologic Cycle, Condensation, Precipitation, Evaporation, Transpiration, Carbon-Oxygen Cycle, Glucose, Nitrogen Cycle, Energy, Abiotic (nonliving), Biotic (living), biome, biodiversity

1. Put the levels of organization in the proper order:

c. organism speciespopulationcommunity ecosystem

2. An ecosystem includes all the biotic and abiotic factors in an environment.

3. How do each of these organisms get their energy?

a. Producer – captures energy from the sun (photosynthesis) or, less commonly, a chemical (chemosynthesis) and uses it to make their own food.

b. Consumer – procures energy from another organism.

c. Decomposer – a special kind of consumer that obtains its energy by breaking down waste or the bodies of dead organisms.

4. A food chain shows the flow of energy in an ecosystem. A food web is a group of interconnected food webs.

A food chain consists of only one straight line. Here is an example of a food chain:sun corn mouse barn owl

5. Make a food chain using the following organisms: hawk, leaves, robin, caterpillar

sun leaves caterpillar robin hawk

A food web is made up of interconnected food chains. Here is an example of a food web:

corn mousesun owl

insect shrew

berries bird

6. Answer the following questions about this food web:

a. List the producers: corn, berriesb. List the consumers and tell whether each one is an herbivore, carnivore, or omnivore. Also tell

whether the consumer is 1st level (primary), second level (secondary), 3rd level (tertiary), etc. mouse (omnivore) both a primary and secondary consumerinsect (herbivore) primary consumerbird (herbivore) primary consumershrew (carnivore) secondary consumerowl (carnivore) secondary and tertiary consumer

Can a consumer occupy more than one level in a food web? YES! Both the mouse and the owl are examples of a consumer that occupies more than one level in the food web.

7. Create a food web using these organisms. Make sure that the arrows are pointing in the direction of the flow of energy! Don’t forget to start with the sun.

Orca, leopard seal, small fish, zooplankton, phytoplankton, medium-sized fish, krill, penguin, baleen whale

Your web should start with the sun and have an arrow going from the sun to the phytoplankton, which is the producer in this ecosystem. Zooplankton feed on phytoplankton and krill eat both kinds of plankton. The baleen whale, though huge, feeds primarily on krill. Small fish will eat the krill also and many feed on plankton. Larger fish eat smaller fish. Penguins eat smaller fish. Leopard seals eat penguins and larger fish. Orcas will eat penguins and leopard seals and even the whales. Make sure your arrows are pointing in the direction that the energy flows.

8. Explain what would happen to the organisms in this food web if ozone depletion caused a decrease in marine phytoplankton.

Your explanation should have pointed out that due to the interconnections and feeding relationships, that if the phytoplankton (the producer in this ecosystem) decreases, then all higher levels will be negatively affected. There will be a decrease in all populations and a possibility that this ecosystem could collapse.

9. Define:a. carnivore: A consumer that gets its energy and nutrients from eating other consumers.

b. herbivore: A consumer that gets its energy and nutrients by eating producers.

c. omnivore: A consumer that gets its energy and nutrients by eating both consumers and producers.

d. scavenger: An animal that gets its energy and nutrients by eating dead animals or waste. (Slightly different from a decomposer, which usually isn’t “eating,” but breaking down. However, sometimes the line between decomposer and scavenger is blurry, such as with worms or maggots. Usually the term scavenger refers to something like a hyena or vulture.)

e. predator: An animal that hunts and kills another animal for its food.

f. prey: An animal that is hunted and killed by another animal for food.

10. What does the root “vore” mean? eating (It comes from the Latin word “vorare,” which means to devour. Another word that comes from this root is voracious, as in, “After she ran the 5K, she had a voracious appetite.”)

11. Which of the following statements describes the energy changes involved in an ecosystem?

(a) The largest animals usually provide the energy for smaller animals and for plants in a given ecosystem? (b) The sun’s energy is made available to an ecosystem by the producers in that ecosystem.(c) The energy for living plants in an ecosystem comes mainly from dead animals, which are broken down by decomposers.(d) In an ecosystem, the smaller organisms require more energy than larger organisms.

12. What do the arrows in a food chain or food web indicate? Flow of energy

13. When a predator species is eliminated from the ecosystem, which of the following is likely to happen?

(a) The number of prey will increase and the amount of vegetation will decrease. (b) The number of prey will decrease and the amount of vegetation will increase. (c) The number of prey will decrease and the amount of vegetation will decrease. (d) The number of prey will stay almost the same and the amount of vegetation will increase.

14. Fill in the blanks: Energy flows through an ecosystem once, while matter cycles through ecosystems over and over.

15. Photosynthesis is the process by which producers capture the sun’s energy and manufacture food (glucose) from it. Write the word equation for photosynthesis:

Write the chemical equation for photosynthesis:

16. Respiration is the process by which organisms release the energy stored in food (glucose) in order to use it to carry out their life processes.

Write the word equation for respiration.

Write the chemical equation for respiration.

17. Make a simple diagram of the hyrdrologic (water) cycle. Use the following terms to label it:evaporation, condensation, precipitation, infiltration, groundwater, surface water, run-off, transpiration

Note: I found a diagram on line. It uses the term evapotranspiration, which is interchangeable with transpiration.

Important: Earth is not getting any new supplies of water. The same water is recycled over and over and over.

18. 78% of the earth’s atmosphere is composed of nitrogen, which is a requirement of living things, yet most organisms are unable to utilize gaseous nitrogen. How do organisms procure nitrogen?

Gaseous nitrogen must be “fixed,” or changed into a different form by bacteria, which may be in the soil or in the nodules of certain plants (legumes). It can also be added to the soil by lightning. When it is in the form of nitrates or nitrites, plants can take it up and use it. Animals get their nitrogen by consuming plants or other animals. Nitrogen is the basic building block of protein. Like all materials, nitrogen is cycled through ecosystems over and over. Here are a couple diagrams of the nitrogen cycle.

19. Draw a diagram of the Carbon-Oxygen Cycle in this space. Here’s a simplified version:

Here are some more complicated versions. One concentrated on Carbon and the other Oxygen, but these two materials’ cycles are intertwined.

How is human activity causing this cycle to become unbalanced? Humans are adding more Carbon dioxide to the atmosphere by burning fossil fuels. They are also decreasing the amount of oxygen added to the atmosphere by deforestation.

Important: CO2 is considered a “greenhouse gas” because its presence in the atmosphere helps trap heat energy.

Which environmental problem is being exacerbated by excess emissions of CO2 from human activity, such as the burning of fossil fuels? Global Climate Change (often referred to as Global Warming, but the first term more accurately describes the problems being caused by an overall increase in average global temperatures.)

20. Some environmental problems that are facing humankind in the 21st century are listed here:

a. global warming (more accurately called global climate change)

b. ozone depletionc. habitat destructiond loss of species diversitye. air and water pollutionf. solid waste disposal

ENVIRONMENTAL ISSUES: Many people confuse global warming with ozone depletion. These are two different issues:

Global Warming (aka Global Climate Change) is caused by increased levels of greenhouse gases. The “greenhouse effect” in and of itself is not bad – it is what keeps Earth’s temperatures warm enough for living organisms to survive here. However, increasing the concentrations of CO2 and other heat-trapping gases is causing the average global temperatures to rise. This in turn is causing the melting of glaciers, a rise of sea level, and changes in ocean and wind currents, which will likely result in flooded coastal areas, more severe storms, more severe droughts and increased desertification (with resulting food and water shortages), and loss of species diversity.

Ozone Depletion Ozone (O3) is a molecule made up of 3 atoms of oxygen instead of two, which is Oxygen gas (O2). It is found in the upper atmosphere of Earth and protects living organisms from harmful ultraviolet radiation. Certain molecules produced by human activity, such as CFCs, react with ozone to break it up. As a result, holes in the ozone layer have formed, particularly over polar regions. Since the ban of CFCs, the holes in the ozone layer have been getting smaller. This is an example of how people really can make changes that have a positive effect on the environment

Biodiversity Crisis: Biodiversity generally refers to the number of different species in an area, but on a different scale, it also refers to the genetic diversity within a specific population. Biodiversity is important because it has both economic and ecological value. Not only that, healthy, functioning ecosystems provide us with crucial ecosystem services, such as drinkable water and breathable air. Without these services, living organisms, including human beings, cannot survive. Biodiversity is currently being threatened by poaching, pollution, the introduction of exotic species, but most especially by habitat destruction. In addition, the remaining habitats are being broken into smaller, isolated fragments, which also makes the organisms living there very vulnerable. In addition, global climate change, discussed above, is having a negative impact on biodiversity. The extinction rate has increased to an alarming rate, with still more organisms threatened or endangered. Some ways we can help protect biodiversity are captive breeding, enacting laws and treaties, and preserving and restoring habitat.

Standardized Test Practice: Ecology

1. The major cause of extinction today is

A. poachingB. pollutionC. habitat destructionD. introduction of exotic species

2. In some areas, foresters plant one tree for every tree they cut. This activity is an example of a

A. nonsustainable approach to a nonrenewable resource.B. a sustainable approach to a nonrenewable natural resource.C. a nonsustainable approach to a renewable resource.D. a sustainable approach to a renewable resource.

3. A freshwater lake has a muddy bottom, which is home to different types of algae and other organisms. Many species of fish feed on the algae. Which of the following is an abiotic feature in this ecosystem?

A. the temperature of the waterB. the color of the algaeC. the number of species of fishD. the amount of food available to the fish

4. In general, which of the following is a true statement about population size?

A. If birth rate < death rate, population size increases.B. If death rate < birth rate, population size decreases.C. If birth rate > death rate, population size increases.D. If death rate > birth rate, population size increases.

5. Geothermal energy is not a widely used source of energy because

A. dams can have a negative effect on the environment.B. methane gas is produced as a waste product.C. it is difficult to store.D. magma only comes close to Earth’s surface in a few locations.

Geology: The Study of Earth and its Processes

Key Concept: Earth is a dynamic planet that is always changing.Key Terms: constructive forces, destructive forces, lithosphere, asthenosphere, continental drift, pangaea, convection, plate tectonics, convergent boundary, subduction, divergent boundary, transform boundary, hot spot, sea-floor spreading, ring of fire, magma, lava, earthquake, fault, focus, epicenter, moment magnitude

1. Diagram the layers of the earth. Check your diagram by looking at fig. 8-11 on p. 195 of your review book.

2. What layers of the earth make up the plates? The crust and the uppermost, rigid layer of the mantle together make up the lithosphere. The lithosphere is broken up into the tectonic plates.

3. What mechanism causes the plates to move? Draw a diagram and describe. Geologists believe that convection currents in the mantle cause the rigid plates to slide along top of the more plastic asthenosphere. The currents are caused by heat from the core.

4. Draw arrows to indicate the movement of plates at each of the three types of plate boundaries:

a. transform

b. convergent

c. divergent

5. Explain what is most likely to happen at each of the following types of plate boundaries?

a. Transform boundary: earthquakes

b. convergentcontinental crust vs. oceanic crust – subduction (o.c. under c.c.) causes formation of an oceanic

trench and chain of volcanoes along coast; earthquakes common.

continental crust vs. continental crust – mountain-building; no volcanism; earthquakes common.

oceanic crust vs. oceanic crust – subduction (older, denser crust dives beneath other one) volcanoes & earthquakes; oceanic trench and chain of volcanic islands will form; earthquakes common.

c. divergentcontinental crust – rift valley forms; volcanoes & earthquakes

oceanic crust – mid-ocean ridge forms; sea-floor spreading occurs (formation of new crust). Volcanoes and earthquakes.

6. There are three ways that mountains can be formed. Explain how each one occurs:

a. fault-block mountains – Fault-block mountains are formed from faulting – any break in the earth’s crust – which is in term formed by stress. In the picture on the left, tension stress forms normal faulting. The footwall is upthrust to form a mountain. In the picture on the right, compression stress forms a reverse fault. The hanging wall is thrust upward to form a mountain.

b. folded mountains – Folded mountains are formed by compression stress also, but this time there is no

faulting. Instead, the rock is deformed rather than broken.

c. volcanic mountains These mountains make themselves! Every time they erupt, the layers of lava and/or ash cool and harden to gradually build the mountain.

7. Even though volcanoes seem very destructive to us, they are actually a constructive force, geologically speaking. How can this be so? Volcanoes are geologically constructive forces because they make new land.

8. What is sea-floor spreading and how does it provide evidence to support the Theory of Plate Tectonics? Sea-floor spreading is the creation of new crust at the mid-oceanic ridge. As magma rises at a divergent plate boundary beneath the sea, it cools to form new crust. The new crust pushes the old crust away on either side of

the rift. Geologists know that new crust is forming because of the increasing age of the rock as it is farther away from the rift. Since the planet is not getting any bigger, crust must be being destroyed elsewhere. This phenomenon supports the theory that the lithosphere is broken into a series of plates that are in constant motion.

9. What causes Earth to have a magnetic field? Geologists believe that because the earth is spinning, currents form in the liquid outer core, which is composed primarily of nickel and iron. This flow of liquid iron generates electric currents, which in turn produce magnetic fields. Charged metals passing through these fields go on to create electric currents of their own, and so the cycle continues. This self-sustaining loop is known as the geodynamo. The spiralling caused by the Coriolis force (inertial force caused by rotation of Earth) caused the separate magnetic fields created to roughly align in the same direction, their combined effect adding up to produce one vast magnetic field engulfing the planet. The currents are not consistent, which is why the magnetic poles switch places every half million years ago. Geologists think we’re do for another flip soon: in a few thousand years or so – that’s soon in geologic time!

10. How do geologists know what the inside of the earth is like if we cannot go there? (see fig. 8 – 10 p. 194)Geologists are able to infer the structure and composition of the Earth’s interior by studying the behavior of seismic waves. The two main kinds of seismic waves are primary (p) waves and secondary (s) waves. Primary waves are compressional. They are faster than s waves and can pass through any substance. Secondary waves move side to side, they are slower, and they can only pass through solids.

HUMAN BODY

Key Concept: The human body is organized in a hierarchical fashion. All the components work together.

levels of organization:

CELLS TISSUES ORGANS ORGAN SYSTEMS ORGANISM

CELLS: Shape, size, and structure contribute to function

e.g. neurons have long thin projections to carry messages cardiac muscle contracts (heartbeat)

TISSUE = a group of similar cells that perform the same function

ORGAN = a group of tissues working together to perform a particular function

e.g. heart, kidney, lungs, stomach, brain

ORGAN SYSTEM= group of organs working together to perform a specific life process

ORGANISM = the entire human body relies on all its organ systems to work together to sustain good health and proper functioning

Organ Systems: organ system function e.g. of organs or parts

skeletal provides support; protects internal organs

skull, ribs

muscular moves organs & body parts bicep, quadriceps

nervous controls body activities; carries and interprets messages

brain, spinal cord

endocrine regulates body activities via hormones adrenal glands, pituitary glanddigestive breaks down food into usable form stomach, intestines

circulatory carries needed materials to body cells and waste material away

heart, arteries, veins

respiratory exchanges gases with environment lungs, bronchi, alveoli

excretory removes waste from body kidneys

reproductive produces offspring ovaries, testes

skin (integumentary)

Protects body; keeps water inside the body; helps regulate body temperature

skin, sweat glands, oil glands

immune Protects body from disease-causing agents

white blood cells, thymus, spleen, lymph nodes

Note: When I copied this table, I left off the immune system! Sorry about that. I added it here.HOMEOSTASIS= the maintenance of a constant internal environment

Organisms respond to changes in their internal and external environment in order to regulate their body processes and thus maintain homeostasis.

examples of regulation:o when you’re hot, you sweato when your body gets low on water, you feel thirsty

Some processes:RESPIRATION – release of energy stored in food; necessary for all bodily functions, (requires oxygen and glucose; gives off carbon dioxide and water)

EXCRETION – process of removing waste

REGULATION – process by which organisms respond to changes in their internal or external environments

REPRODUCTION – process by which an organism produces new individuals (offspring)

GROWTH - an increase in size (new cells are made)

DEVELOPMENT – changes in the organism as it gets older

NUTRITION – includes INGESTION = taking in foodDIGESTION = the physical breakdown of nutrients*ELIMINATION = the removal of undigested food from the body

*Nutrients and their uses:Proteins – supply materials needed for growth and repairCarbohydrates (Sugar & starches) – provide quick energyFats & Oils – provide stored energy; required for some life processesVitamins – assist life processes; prevent diseaseMinerals – supply materials for growth and repair; help carry out life processes.

There are over 100 trillion cells in your body and at least 100 different types of cell. Find pictures of different kinds of cells and draw them in this space. IMPORTANT: Specialized cells perform specialized functions.

Standardized Test Practice: Read the passage, then answer the questions:

Your nervous system and endocrine system work together to help keep your body healthy. Your brain, which is part of your nervous system, constantly monitors different conditions inside your body. If your blood is low on water, your brain sends a signal to an organ of the endocrine system, which then releases a chemical that brings the water level in your blood back up top normal. If you get cold, your brain sends a signal to another organ in the endocrine system, which releases a chemical that tells your cells to become more active. The activity of your cells heats up the inside of your body.

1. Which general process does this paragraph best describe?A. Maintaining homeostasisB. Sensing a strong stressorC. Preparing for the “flight-or-flight” responseD. Dealing with long-term stress

Astronomy: The Study of SPACE

Key Concepts: The universe is a very, very, very, very, very, very, very, very, very, very, very, very big place.Most of space is empty space. KEY TERMS: rotation, revolution, orbit, axis, ellipse, planet, dwarf planet, asteroid, comet, meteoroid, Oort Cloud, Kuiper Belt, high-mass star, supernova, red giant, black hole, average-mass star, constellation, circumpolar, seasonal constellation, astronomical unit, light-year, neutron star, equinox, solstice, radio telescope, optical telescope, galaxy, Big Bang Theory, electromagnetic radiation, speed of light, geocentric, heliocentric, terrestrial planet, gas planet, satellite, eclipse (solar vs. lunar), gravitational attraction, tide (neap and spring), moon phases.

1. What causes the seasons on Earth? Diagram and explain. Seasons are ultimately caused by the earth’s axial tilt. As the earth revolves around the sun, at different points in its orbit, the light from the sun is more direct and concentrated in either the northern or southern hemispheres. At other points, the two hemispheres receive equal amounts of sunlight.

2. What causes tides on Earth? Diagram and explain. (see page 246 of Review Book to check)Gravitational pull of moon, and to a lesser extent, that of the sun.

3. Why do we see phases of the moon?

September Equinox

December Solstice June Solstice

March Equinox

ANSWER: The relative position of the sun, earth and moon. Draw and label the phases of the moon in this space:

4. What would happen to tides if the earth-sun-moon always stayed in the same alignment?

(a) We would not experience tides on Earth. (b) Tides would continue following their current pattern. (c) The high and low tides would occur at the same time every day. (d) There would be no low tides – only high tides.

5. Compare the life cycle of an average-mass star, such as our sun, to a high-mass star. Diagram and explain.

6. Why would you weigh less on the moon than you do on Earth?

Since the moon has a smaller mass than Earth and gravitational attraction depends on mass and distance, the strength of the moon’s gravitational pull will not be as strong. It is about 1/6 that of Earth.

IMPORTANT: Gravity is everywhere! Everything that has mass exerts a gravitational attraction on everything else that has mass.

7. Describe how our solar system formed. About how long ago did this happen? (see page 229 of review book)About 4.6 billion years ago, our solar system formed from a nebula, which is a cloud of dust and gas in space. This nebula was the leftover material from the supernova of an older, larger star. Some kind of disturbance caused it to start collapsing in on itself. Because of gravity, the mass in this nebula would have been attracted towards the center. Due to inertia, as the mass was drawn to the center, the material in the nebula would flatten into a disk and spin. Just like a spinning figure skater’s speed increases when she pulls in her arms, as the debris continued to be drawn to the center, the spinning would have increased. Most of the mass (99.99% of it!) formed the sun at the center of the infant solar system. Other debris formed planetisemals, proto-planets, and eventually planets through the process of accretion. It was kind of like a demolition derby in the early solar system, which objects slamming into each other to form larger objects. Due to increasing pressure, the proto-sun was getting hotter and hotter. When internal temperature gets high enough, thermonuclear fusion began. This is the process where Hydrogen atoms fuse together to form helium atoms, releasing tremendous amounts of heat and light. When this happened, a star was born. Our newly born sun began to emit what is called the solar wind, which is a stream of energized, charged particles. This rushes out in all directions from the sun, forcing all the miscellaneous debris in between and among the planets to be blown out in all directions. Here is another explanation directly copied from the website “Windows to the Universe”:Scientists believe that the solar system was formed when a cloud of gas and dust in space was disturbed, maybe by the explosion of a nearby star (called a supernova). This explosion made waves in space which squeezed the cloud of gas and dust. Squeezing made the cloud start to collapse, as gravity pulled the gas and dust together, forming a solar nebula. Just like a dancer that spins faster as she pulls in her arms, the cloud began to spin as it collapsed. Eventually, the cloud grew hotter and denser in the center, with a disk of gas and dust surrounding it that was hot in the center but cool at the edges. As the disk got thinner and thinner, particles began to stick together and form clumps. Some clumps got bigger, as particles and small clumps stuck to them, eventually forming planets or moons . Near the center of the cloud, where planets like Earth formed, only rocky material could stand the great heat. Icy matter settled in the outer regions of the disk along with rocky material, where the giant planets like Jupiter formed. As the cloud

continued to fall in, the center eventually got so hot that it became a star, the Sun, and blew most of the gas and dust of the new solar system with a strong stellar wind. By studying meteorites, which are thought to be left over from this early phase of the solar system, scientists have found that the solar system is about 4600 million years old!

Here is a link to a video explanation by the great Stephen Hawking: https://www.youtube.com/watch?v=Uhy1fucSRQI

8. Compare the length of planetary day (rotational period) and length of planetary

year (revolutionary period) on the different planets of our solar system. The closer to the sun a planet is, the shorter the revolutionary period and the longer the rotational period – the farther away, just the opposite.

WHAT CAUSES THE SEASONS? ANSWER: THE EARTH’S TILT

The hemisphere that is tilted away from the sun experiences winter.

The hemisphere that is tilted toward the sun experiences summer.

COMMON MISCONCEPTION: The earth experiences the seasons because it is farther away from the sun in the winter and nearer to the sun in the summer.

WHY THIS MUST BE WRONG: The Northern hemisphere has winter while the Southern hemisphere has summer and vice-versa. The distance form the earth to the sun does vary somewhat, but this is not the reason for the seasons. In fact, the earth is actually closer to the sun during winter in the Northern Hemisphere. When the sun shines on the part of the earth that is tilted away from it, its rays are more diffuse and less concentrated than when it shines on the part that is tilted toward it. (See fig. 1)

RELATED CONCEPTS:

Equatorial regions do not have seasons because they never tilt toward or away from the sun. Days and nights are always equal. Temperatures are similar all year ‘round.

During the spring and fall, the earth is tilted sideways in relation to the sun. Days and nights are equal at the spring (vernal) and fall (Autumnal) equinoxes. Label the following on this diagram: June Solstice, December Solstice, Autumnal Equinox, Vernal Equinox.

March Equinox

June Solstice

December Solstice

March Equinox

Summer Solstice: considered the “first day of summer” around June 21st in the Northern Hemisphere longest day of the year shortest night of the year after this day, the days get gradually shorter and the nights longer…

Fall (Autumnal) Equinox: considered the “first day of fall” around Sept. 21st in the Northern Hemisphere day and night are equal sun rises almost exactly in the East and sets almost exactly in the West the days continue to get shorter and the nights get longer until…

Winter Solstice: considered the “first day of winter” around Dec. 21st in the Northern Hemisphere shortest day of the year longest night of the year after this day, the days start to get gradually longer and the nights shorter

Spring (Vernal) Equinox: considered the “first day of spring” around March 21st in the Northern Hemisphere day and night are equal sun rises almost exactly in the East and sets almost exactly in the West the days continue to get shorter and the nights get longer until the summer solstice.

WHAT CAUSES THE TIDES?

ANSWER: THE GRAVITATIONAL ATTRACTION BETWEEN THE EARTH, MOON AND SUN.

Draw a diagram here. See previous page – sorry about the repeat!

spring tides – greatest difference between high and low tides - occur when sun, earth, and moon aligned

neap tides – smallest difference between high and low tides -- occur when sun, earth, and moon are at right angles to each other

WHAT CAUSES AN ECLIPSE?

ANSWER: SUN, EARTH, AND MOON ARE DIRECTLY LINED UP. TWO KINDS:

A. SOLAR ECLIPSE – The moon blocks the light from the sun – only along the pathway of the moon’s shadow!!! (Draw a diagram here.)

In order to see the total eclipse, a person needs to be located in the darkest parts of the moon’s shadow, called the umbra. The diagram below shows what happens when the moon is lined up perfectly and not-so-perfectly.

Remember, the moon is much smaller than the sun! It has to be in the exact, perfect position to cause a solar eclipse.

B. LUNAR ECLIPSE – The earth casts its shadow upon the full moon – only can be viewed from certain locations on Earth! But it can be viewed anyplace where the moon is in view. Lunar eclipses are more common than solar eclipses, plus they are more widely visible, which is why more people get to see a lunar eclipse than a solar eclipse. (Draw a diagram here.)

Why doesn’t an eclipse occur during every full and new moon and why can’t eclipses be seen everywhere on earth? The plane of the moon’s revolution around the earth is tilted at a slight angle (5 degrees) from the plane of the earth’s revolution around the sun.

Eclipse trivia:

1. Lunar eclipses occur more frequently than solar eclipses.2. If you look directly at a solar eclipse, you can permanently damage your eyes!3. During a lunar eclipse, you can still see the moon, but it is dimmer. Often it appears reddish.4. During a solar eclipse, scientists are able to study the sun’s corona, since this is the only time it can

be observed. NOTE: The moon completes one rotation in the same time it takes it to complete one revolution around the earth. As a result, the same side of the moon always faces toward the earth.

COMMON MISCONCEPTION (Sorry, Pink Floyd!): There is no “dark side of the moon” any more than there is a “dark side of the earth.” Just like Earth, half of the moon is always lit by the sun and half of the moon is always in the dark. There is a “far side of the moon.” Only a few NASA astronauts have ever seen it in person, but they did bring back photographs for the rest of us.

Standardized Test Practice for Astronomy:

1. You observe a thin crescent moon in the western sky during the early evening. About two weeks later, a full moon is visible in the eastern sky during the early evening. Which conclusion is best supported by these observations?

A. The moon revolves around the earth.B. The moon rotates on its axis.C. Earth revolves around the sun.D. Earth’s axis is tilted relative to the moon.

2. Only one side of the moon is visible from Earth because

A. The moons does not rotate on its axis.B. The moon does not revolve around the earth.C. The moon rotates faster than it revolves.D. The moon revolves once and rotates once in the same period of time.