2- The Top and bottom of the leaf is covered by thin layer of cells called epidermis that allow sunlight to easily pass into the middle of the leaf.

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1 Final exam summary sheet Topic 5, lesson 2 How leaf is adapted to carry on photosynthesis? 1- Waxy layer called the cuticle cover the leaf slow the water loss. 2- The Top and bottom of the leaf is covered by thin layer of cells called epidermis that allow sunlight to easily pass into the middle of the leaf. 3-In the middle of the leaf there are thin tall cells where photosynthesis takes place, they absorb much of sunlight that enters the leaf, they contain chloroplasts that plant needs to make sugar. 4-The veins of the leaf contain the xylem and phloem, water and minerals enter to the leaf through the xylem, sugar made moves from the leaf to the rest of the plant through the phloem. 5-Below the tall cells, layers of widely spaced cells the air spaces surrounding the cells allow carbon dioxide that is needed during photosynthesis to move freely throughout the leaf. 6- Most leaves have more stomata on the lower epidermis, less light reaches under the leaf so lower part is cooler and less water is lost through transpiration. 1

2 Are there more chloroplasts on the upper part or lower part of the leaf? WHY? On the upper part because chloroplasts use sunlight to carry on photosynthesis and as more sunlight reaches the upper part so more chloroplasts are needed there. Energy from food : On the sunny days, plants make more glucose than they need. What happens to the extra glucose? Plants change the extra glucose into starch which is a form that can be stored by them. When they need the stored food, plants must break down food to release the stored energy. Cellular respiration : Is the process by which all organisms break down glucose to release the stored energy. It happens in the mitochondria in the cytoplasm of cells. The mitochondria uses oxygen to further break down the glucose into simpler substances (carbon dioxide and water ) and energy is released. 2

3 Glucose + oxygen Carbon dioxide + water+ energy Explain, Mitochondria is called The powerhouse of the cell. Because mitochondria releases energy from glucose in the process of cellular respiration. Carbon dioxide- oxygen cycle : 1-Photosynthesis : (Chlorophyll) Carbon dioxide + water Glucose + oxygen (light energy) 2-Cellular respiration : Glucose + oxygen carbon dioxide +water+ energy 3

4 (The processes are the reverse of each other ) The materials needed during one process are the same materials needed for the other process. Both cellular respiration and photosynthesis form the carbon dioxide oxygen cycle. -Respiration : Both plants and animals use oxygen to change energy in food to energy they can use and give off carbon dioxide. -Photosynthesis : Plants use carbon dioxide and energy to produce food So this cycle assure that living things don t run out of the oxygen and carbon they need. Responding to environment: Why do stems grow upward and roots grow downward? (Because plants like other organisms respond to environment) It is not easy to notice. They are not like animals having nerves that control their behavior. Instead chemicals make different parts of the plant grow at different rates. Tropism : Is plant behavior toward or away from something in the environment. phototropism Geotropism Thigmotropism Is a response to light, growing chemicals cause stem to bend toward light, roots bend away from the light. Is a response of the plant to gravity. Even in dark, corn germinates with its seed grow upward and stem downward Is a response to touch, plant with positive thigmotropism grows toward surface it touches, plants with negative thigotropism grow away from surface it touches 4

5 Topic 19 : Lesson 1: What are the characteristics of Earth s sun and Moon? Our sun : 1-It is a star, appears larger than other stars because it is so much closer than others to the earth. 2- It appears as a ball of fire.but it is not burning. 3-About three quarters of the Sun's mass consists of hydrogen, while the rest is mostly helium. 4- Hot gases are called plasma.plasma is so hot that it glows. - he inner core of the sun is dense core ith te erature about 6- Reactions among particles in the core releases energy, that provides light and heat to the earth. 7-Life couldn t exist on Earth ithout energy fro the sun. ( hy?) Without sun Earth would be cold lifeless rock. 8- Sun has no solid surface, outside of the core are swirling layers of plasma. Huge loops of gases called Prominences extends for thousands of kilometers out from the sun. Some prominences are held in place for weeks others explode into space. Intense releases of energy fro the sun s surface are called solar flares.energy from these flares sometimes reaches Earth. This energy cause beautiful light displays called auroras seen near Earth s oles. Earth s moon On clear nights, you can see the moon shinning, but actually no light on the moon. 5

6 he light e see is a sunlight that reflects off the oon s surface. It is unlike the sun formed of swirling hot plasma, the moon is like a giant rock in space, it has almost no atmosphere. The moon rotates (spins on its axis while it revolves around the earth.) Revolve: move on a path around an object. Its same side always faces Earth.(Why?) We see only one side of the moon. Because the time for one rotation and one revolution of the moon are the same as Earth days. Each time it revolves around the Earth it also rotates one time. Phases of the moon If you look at the moon each night for a month You see that it seems to change shape. he Moon doesn t really change in sha e. The MOON has different phases (the different shapes that the moon seems to have ) The shapes change because the size of the lighted part that we can see from the earth changes. Only the half of the moon that faces the sun at any time is lighted. The phases we see depend on the position of the Moon, Earth and the sun. 1. New Moon The Dark phase of the moon The Moon's side facing the Earth is not lighted The Moon is not visible. 6

7 On nights just after a new moon, the moon begins to wax. Waxing means gradually growing larger The moon is waxing when more of its lighted part can be seen each night. 2. Waxing Crescent The Moon appears to be partly but less than one-half illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is increasing. 3-First quarter As the moon continue to wax we can see half of the moon lighted. 4. Waxing Gibbous The Moon appears to be more than one-half but not fully illuminated by direct sunlight 5. Full Moon The Moon's illuminated side is facing the Earth. The Moon appears to be completely illuminated by direct sunlight. 7

8 On nights after a full moon the moon begins to wane Waning means gradually becoming smaller The moon is waning when less of its lighted part can be seen each night. It continues to wane till we see a new moon again and the cycle continues. Complete cycle of moon phases occurs every 29.5 days. 6. Waning Gibbous The Moon appears to be more than one-half but not fully illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is decreasing. 7. Last Quarter One-half of the Moon appears to be illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is decreasing. 8. Waning Crescent The Moon appears to be partly but less than one-half illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is decreasing. 8

9 Learning about the moon 1- The first visit to the moon by a spacecraft happened at 1957 by unmanned soviet craft Luna 2 Landed on the surface of the moon. 2- After ten years, Apollo 11 astronuts ( Buzz and Armstrong ) landed on the moon. 3- Then they landed five more landings ended on (Moon has no atmosphere, from the features of the moon s surface they determined its age ). Comparing sizes: The sun and The Earth Width Sun is two hundred times wider than Earth How many earth fit in the sun If the sun is hollow, more than one million earths can fit inside the sun. Mass The mass of the sun is about 330,000 times the mass of the earth Gravitational pull The gravitational pull is 30 times greater than on Earth s surface 9

10 Which revolve around which? People used to think that sun travels round the Earth. We now know that the sun is the center of our solar system and that Earth and other planets revolve around the sun. Earth orbits the sun every 365 1/4 day Earth rotation: Earth rotates around its axis. Rotates ( spins around its axis ). Axis : is an imaginary line between its poles. As the sun rises in the eastern sky, sunlight begins to warm Earth. Heat from the sun is most intense around the noon when the sun is at its highest point. In the evening, the sun appears to sink below the western horizon. At midnight, the side of Earth opposite to you experience the noon sun. A day : is the time for a planet to make one complete rotation. Earth spins from the east to the west.(that s why sun appears to rise above the eastern horizon ). We experience daytime as long as the sun is visible fro your location on the Earth. Daytime ends when Earth has turned enough that the sun seems to set in the west. Night time is when the sun is no longer visible to us. The number of hours of daylight changes throughout the year. (If we wake up in the winter morning, it may be still dark outside while if you wake up on the summer morning it may be lighted outside for hours ). The earth is tilted by an angle of 23.5 toward the sun, that side that is slightly tilted toward the sun has more day light hours and fewer nighttime. 10

11 Effect of Earth s Axis tilt on the poles : Northern hemisphere is tilted away from the sun so the day hours are less than the night hours. The southern hemisphere is tilted toward the sun and the day hours are more than the night hours At the equator it is 12/12 hours. Day light and darkness at the poles each last six months. Sometimes we notice the moon during the day. The Moon can be seen whenever it is on your side of Earth this is sometimes during daytime and something during daytime. During the year, the seasons change depending on the amount of sunlight reaching the Earth as it revolves around the Sun. The seasons are caused as the Earth, tilted on its axis, travels in a loop around the Sun each year. Summer happens in the hemisphere tilted towards the Sun, and winter happens in the hemisphere tilted away from the Sun. As the Earth travels around the Sun, the hemisphere that is tilted towards or away from the Sun changes. The hemisphere that is tilted towards the Sun is warmer because sunlight travels more directly to the Earth s surface so less gets scattered in the atmosphere. That means that when it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere. The hemisphere tilted towards the Sun has longer days and shorter nights. That s why days are longer during the summer than during the winter. 11

12 In general, the further away from the equator you travel, the cooler summer and winter temperatures become. At the equator there are no seasons because each day the Sun strikes at about the same angle. Every day of the year the equator receives about 12 hours of sunlight. The poles remain cool because they are never tilted in a direct path of sunlight. Much light is scattered by the atmosphere before reaching the Earth surface at the poles. During midwinter, when a pole is tilted away from the Sun, there is no daylight at all. The sun never rises! However, during the summer, a pole receives sunlight all the time and there is no night! Late June : he north end of the Earth s axis is tilted to ard the sun, it is summer in the northern hemisphere and southern hemisphere is winter. Late September :neither hemisphere is pointed toward the sun so it is fall in the north and spring in the south. Late December :the northern pole is away and the south is toward the sun. Late March : neither hemisphere is pointed toward the sun. 12

13 In summer : 1- At the noon the sun s rays oint directly to ard us, the shado is very s all, days are very warm. 2-As days passes, the sun rays become scattered, the shadow becomes longer, days are less warm. 3- We have winter when the earth is tilted away from the sun, the sun rays are scattered, shadows are longer. Solar Eclipse Solar come from the Latin word sol meaning sun How are earth, the sun and the moon lined up during a solar eclipse? The sun, the moon and earth, the moon is in between ( How this happens?) The earth move around the sun in an orbit, and the moon moves around the earth in another orbit that is tilted at an angle When the moon orbit passes between the sun and the moon, the moon eclipses or covers the sun A solar eclipse happens when the moon blocks the light of the sun. The moon makes two types of shadows on earth during eclipse The Umbera : is the dark inner part of eclipse shadow. The penumbera : is the lighter, outer part of eclipse shadow. 13

14 Although it occurs several times a year, each place on earth can experience one every few hundreds of years. During solar eclipse, places on earth may experience, total, partial, or no eclipse at all. Total eclipse : is when the umbera passes over an area.( the sun is completely blocked from view for several minutes, the sky darkens, and stars are visible in day time ) As the moon shadow is small only small area experience total eclipse. The partial eclipse : occur when the umbera misses the earth and only the penumbera passes over an area. We shouldn t look directly to the sun, we can use two cardboard, one is placed on the ground and the other we make a pinhole on the center, then point the pinhole at the sun so u can see around image on the other card board ( the sun ) Lunar Eclipses : It occurs during the full moon when earth is between the sun and the moon. It ha ens hen the oon asses through the earth s shado. Total lunar eclipse can happens for hours while the partial lunar eclipse is shorter. Unlike the solar eclipse, a lunar eclipse can be seen by most parts of the earth.(why?) Why can more people see a lunar eclipse than a solar eclipse? During lunar eclipse, the shadow cast on the moon by the earth which is much larger than the shadow cast on earth by the moon during a solar eclipse. 14