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•You hear that a pinch of soil may contain millions of organisms. •What optical tools would you use to see these organisms and to study their structure? What is the structure of a cell?

7th Grade science 1st Semester Review

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7th Grade science 1st Semester Review

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What is the structure of a cell?

You hear that a pinch of soil may contain millions of organisms. What optical tools would you use to see these organisms and to study their structure?

Section 1: Discovering CellsWhat are cells? How did the invention of the microscope contribute to knowledge about living things? What is the cell theory? How are the cells of multicellular organisms organized?

Development of the Cell TheoryThe cell theory states the following: All living things are composed of cells. Cells are the basic units of structure and function in living things. All cells are produced from other cells.

Unicellular and MulticellularUnicellular, or single-celled, organisms include bacteria, the most numerous organisms on Earth. Multicellular organisms are composed of many cells.

Unicellular

Multicellular

Plant and Animal Cells

NucleusThe nucleus is the cells control center, directing all of the cells activities.

MitochondrionMitochondria are known as the powerhouses of the cell because they convert energy in food molecules to energy the cell can use to carry out its functions.

Endoplasmic ReticulumThe endoplasmic reticulum is similar to the system of hallways in a building. Proteins and other materials move throughout the cell by way of the endoplasmic reticulum. The spots on this organelle are ribosomes, which produce proteins.

Golgi BodyThe Golgi bodies receive proteins and other newly formed materials from the endoplasmic reticulum, package them, and distribute them to other parts of the cell.

Special Parts PLANT CELLS Chloroplasts Cell Wall Large Central Vacuole

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ChloroplastsOne of the most widely recognized and important characteristics of plants is their ability to conduct photosynthesis, in effect, to make their own food by converting light energy into chemical energy.

Cell Wall

One of the most important distinguishing features of plant cells is the presence of a cell wall. The relative rigidity of the cell wall renders plants sedentary,

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Cells: LOTS of Different Kinds!Here are two examples. Can you guess what kind?

Nerve Cells

Skin Cells

Second Level: TissuesIn any multi-cellular organism, cells rarely work alone. Cells that are similar in structure and function are usually joined together to form tissues. Tissues are the second level of organization.There are four basic/major types of tissues in the human body: Muscle tissue, nerve tissue, connective tissue, and epithelial tissue. (There are other kinds of tissues besides these.) Other kinds of tissueinclude bone tissue (a strong solid tissue that gives you shape and support) made of bone cells in your body form bone tissue. Blood cells in your body are part of blood tissue, a liquid tissue responsible for transporting food and oxygen throughout the body.

Lets Look Again

Here are the cells we saw before, but if you look closely, you can see that they all look similar. Nerve cells working together make nerve tissue, and skin cells make up a special type of epithelial tissue.

Taken One At A Time.Connective tissue connects and supports parts of the body. Blood, fat, ligaments, cartilage, bones, and tendons are all connective tissues. Nerve tissue carries messages back and forth between the brain and every other part of the body. The brain, spinal cord, and nerves are made up of nerve tissue.

Epithelial tissue covers and lines the Muscle tissue can contract, or shorten. surfaces of your body and organs, inside and Because of this, muscle tissue makes out. They primarily serve as protective parts of your body move. barriers. Skin is one example.

Level Three: OrgansWhen a bunch of different types of tissues work together, they form an organ. There are many organs in the body. How many can you name??

GET IT????

Level Four: Organ SystemsEach organ in your body is part of an organ system, a group of organs that work together to perform a major function.

For example, your heart is part of your circulatory system, which carries oxygen and other materials throughout your body. Besides the heart, blood vessels are organs that work in your circulatory system.

The nervous system detects and interprets information from the environment outside the body and from within the body; controls most body functions.

The immune system fights disease. The excretory system removes wastes. The endocrine system controls many body processes by means of chemicals, like hormones.

The muscular system enables the body to move; moves food through the digestive system, and keeps the heart beating.

The skeletal system supports and protects the body, and works with the muscular system to allow movement; makes and stores blood cells and stores some other materials.

The digestive system takes food into the body, breaks the food down into smaller particles, and absorbs the digested materials.

The respiratory system takes oxygen into the body and eliminates carbon dioxide. The reproductive system produces sex cells that can unite with other sex cells to create offspring; controls male and female characteristics.

Lets Review. 1st Level: Cells working together form 2nd Level: Tissues, which can form

3rd Level: Organs, which work together to form 4th Level: Organ Systems, which work together to form 5th Level: Organisms!

Signs of Chemical Changes These changes alter the substance so that a new substance with NEW properties appears and is NOT easily reversible: Unexpected color change or odor Release of heat, light, or sound NOT easily reversible Produces gas or water, or formation of a solid NEW substance, with NEW properties

The Digestive SystemPurpose of the Digestive system: Breaks down food into substances that cells can absorb and use.

How is food digested? Breaking down of food into smaller piece The mixing of food Movement through the digestive tract Chemical breakdown of the large molecules of food into smaller molecules

Mouth Physical Change Mechanical digestion - teeth Chemical digestion saliva Chewing mixes the food with saliva, from salivary glands around the mouth and face, to make it moist and easy to swallow. Enzymes in the saliva begin digestion of carbohydrates.

Stomach Chemical Change The stomach lining produces strong digestive juices. These create chemical reactions in the stomach, breaking down and dissolving its nutrients. Digests proteins and fats in the stomach

Small Intestine - Chemical Enzymes continue the chemical reactions on the food. EX. from the liver bile breaks down fat, and the pancreas insulin breaks down sugar The nutrients are broken down small enough to pass through the lining of the small intestine, and into the blood (diffusion). Digests proteins, fats, and carbohydrates.

Large Intestine (Colon) Absorbs extra nutrients & water Forms wastes into solid feces

Physical Change

Physical or Chemical ChangeBreaking down of food into smaller piece by chewing The mixing of food in mouth with tongue Food Mixing with Saliva Hydrochloric acid breaking down food in the stomach

Enzymes from the live and pancrease breaking down foodin the small intestine Large intestine Forms wastes into solid feces

Force, Motion and EnergyForces that affect motion

Turgor Pressure:Plants cells have larger vacuoles because they have to store all of the food they make.This plant is more rigid!

This plant is more wilted!

If a plant cell is immersed in a solution that has a higher salt concentration than that of the cell, water will leave the cell. The loss of water from the cell will cause the cell to lose the pressure exerted by the water in the plant cells vacuole, which is called turgor pressure.

If the cell membrane becomes damaged, it will lose the ability to control what goes in and out of the cell.

Turgor Pressure in your skin:

Types of tropisms: Phototropism: response to lightThis is why people turn their house plants so they wont lean.

Thermotropism: response to temperatureThe plants leaves curl in response to the temperature.

Hydrotropism: response to waterThe roots grow toward the water

Geotropism: response to gravityThe roots grow downward due to the force of gravity.

Geotropism The growth of a living organism in response to gravity, as the downward growth of plant roots. Roots display positive geotropism when they grow downwards, while shoots display negative geotropism when they grow upwards.

A corn kernel was planted face down and this was the result. You can see how it started to grow downwards and then responded to the external stimulus of the sun and grew upwards.

The root system started to grow upwards toward the sun and then responded to gravity (geotropism) and began to grow downwards.

For a plant to be planted in an upside down planter like this the roots must be started first. Why must the roots must be started first in a regular planter?Well because If you just planted the plant upside down first the roots would grow downward as well which would kill the plant. Geotropism is what would cause the plants roots to grow downward.You must start the plant first so the roots will grow correctly and then just the plant itself will grow downwards.

Emergence of Seedlings:Seeds respond to stimuli (internal and external).Geotropism is where a seed It takes force and and its roots respond to the pressure for the force of gravity. This forces plant to push out the roots to grow downward. of the ground. Is this an internal or external Gravity is an external stimulus! stimulus?

Another external stimuli to the plant is the sun. The plant responds to the sun by growing upwards.

Forces that affect motion A force is a push or a pull. Work is done when a force moves an object. A seedling: pushing up the dirt :: a person: rolling a boulder up a hill

It takes MORE force to move something straight up

LESS force is used to move something up a ramp or inclined plane

Forces that affect motion Seeds sprout because the force of water pressure (also called turgor pressure) inflates the emerging shoot. The force of the shoot straightening pulls the seed leaves above ground.

Forces that affect motion Turgor Pressure, and Tropisms are all forces that affect the motion of plants and its cells.PHOTOSYNTHESIS in plants GEOTROPISM in roots

THERMOTROPISM in HYDROTROPISM plants leaves when it is in roots cold TURGOR Pressure in celery and potato

How does Turgor Pressure Work? OsmosisOsmosis: diffusion of water through a selectively permeable membrane Water moves from high to low concentrations

Water moves freely through pores. Solute (green) to large to move across.

Internal Stimulus A stimulus that comes from inside your body or a plant EX. hunger pains, emotions, and a full bladder vomiting, temperature, dehydration.

External Stimulus Any stimulus from outside the body or plant. Ex. flashing lights, scary or sad events, hot stove. tropisms.

Response A reaction to a stimulus. When you are hungry you eat, when you are sad you cry, when you are scared you run a plant growingor wilting

Internal Stimuli & ResponsesThink of all the changing conditions that an organism might need to respond to. Heres just a sample: And here are some specific responses to these internal stimuli. Forget shivering Wheres my hoodie?!?

External Stimuli & ResponsesExternal stimuli can be a little more complicated. Lets see how. EXTERNAL STIMULUS Bright sunlight Shorter days, colder temperatures Squinting RESPONSE (ok, this one is pretty simple)

Trees drop their leaves in autumn

Increasingly hot weatherSunlight, motion of the Sun. Difficult survival conditions coming up

Dogs shed their thick coats in late springPlants grow toward the Suns position. Hibernation (chipmunks sleep through cold months) Migration (geese fly to warmer weather & easy food) Dormancy (grass turns brown in winter instead of trying to grow & stay green)

There really are countless more examples, from as simple to an itch on your arm to the complicated conditions that cause plants to realize winter is over and fire back into life.

#22 Write.

Stimulus (changing condition) and Response A. Internal Stimulus detected inside an organism ex: hunger, emotions, temperature B. External Stimulus detected outside ex: light, dark, climate changeOrganisms respond to these stimuli to help increase their chances at survival. When you learn more about the human body, you might be astonished to discover the numerous stimuli, both internal and external, that your nerves and brain can respond to.

Looks like Joe is prepared to handle some stimuliYep, sure am.

And dont think I forgot to pack one other thing

Notes

HomeostasisA state of balance in the bodyWhoa

Definition of Homeostasis homeo = same; stasis = standing Homeostasis is the term we use to describe the constant state of the internal environment. Homeostasis is a state of balance in the body.

Introduction You are exposed to ever changing environmental conditions. For example, you may walk out of an air conditioned room into the hot summer sun. However the cells in your body work best when their surroundings are kept constant. Your body has many mechanisms that keep the cells surroundings constant even though your external environment is changing. This is homeostasis. Homeostasis is very important because when it fails you become ill and may die.

Maintaining Homeostasis Chemistry is the reason why we must maintain homeostasis. Biochemical processes (the chemical reactions) that occur within us) are vital to life and occur efficiently only within a limited temperature range and at a specific pH.

Internal Communication The body must have good internal communication, using the endocrine and nervous systems, to maintain homeostasis. Feedback inhibition limits the operation of a system or causes it to shut down when it senses too much of a certain product (such as water, glucose, salt, heat, CO2 etc.) It will cause the system to turn back on when there is too little of this product.

A Temperature Control System To help us understand homeostasis in living organisms, let us first look at a nonliving system. We will use a temperature control system for a room which has many similar features to homeostatic mechanisms. Click on the thermostat.

Human Body Temperature Control You have just studied how the temperature of a room can be controlled. Now you will examine how similar mechanisms operate to control body temperature in humans. Go to this web address. Click on the hot man.

Summary Changes in temp are detected by thermometer, which feeds info about the actual temp back to thermostat. Thermostat has been previously set to ideal (set point) value; thermostat compares actual value to set point value and sends signal to furnace. Furnace fires up and changes the internal temp back toward set point. (Furnace will shut down when thermostat determines actual temp is now higher than set point temp).

Human Example of Negative Feedback Human example: shivering in response to cooling of body during cold weather or sweating when their core temperature gets too hot. Homeostasis allows an organism to remain in balance with its environment. If homeostasis is not maintained, it can harm or kill the organism.

Recognize that radiant energy from the sun is transferred into chemical energy through the process of photosynthesis. 7C The student will demonstrate and illustrate forces that affect motion in everydaylife such as an emergence of seedlings, turgor pressure, and geotropism. Biological forces affect how living organisms grow and develop as well as keep them intact. Turgor pressure in plants is defined as the internal pressure applied in an outward motion against the plants cell walls. Plants are able to stand erect and maintain rigidness because of this pressure/force. When plants react to changes in their environment this is defined as a stimulus response. There are two types of stimulus responses: internal and external. Plant internal stimulus comes from within the organism. An example of internal stimuli is a response such as wilting. Plant external stimulus comes from outside an organism. An example of external stimulus is an organisms response to light such as a plant growing in the direction of its light source.

13B Describe and relate responses in organisms that may result from internal stimuli such as wilting in plants and fever or vomiting in animals that allow them to maintain balance. 13A Investigate how organisms respond to external stimuli found in the environment such as phototropism and fight or flight.