Grade 7 Science Blog

Grade 7 Science Unit 1: Characteristics of Living Things

Grade 7 Science Unit 1 Characteristics of Living Things

Topic 1: Characteristics of Living Things

Biology
· The study of living things
· Includes microorganisms, plants and animals

Characteristics

· Features or traits (Ex. A long neck is a characteristic of a giraffe)

Organisms
· Scientific term for a living thing

Species
· A specific type of living thing that has similar characteristics
· The organisms must be able to reproduce and produce young that can also reproduce (Ex. humans, cats)

Characteristics of Living Things
· All organisms grow.
· All organisms move.
· All organisms reproduce.
· All organisms produce or consume (eat) food.
· All organisms respond to stimuli in their environment.
· All organisms exchange gases.

All Living Things are made of:
· Cells
· Have a special chemical make-up. (Carbon, nitrogen, hydrogen and oxygen)

The only characteristics shared by both living and dead things are:
· They are made of cells.
· They are made of special chemicals.

Reproduction
· The process of making a new generation.

Photosynthesis
· The process where green plants are able to use the Sun's energy to make food.

Stimulus
· Something that causes an organism to respond

Cells
· Building blocks upon which all living things are made.

Living Things
· Organisms that shows signs of life, such as moving growing, reproducing, etc. (Ex. A maple tree)

Dead Things
· Organisms that once showed signs of life but do not any longer (Ex. Leaf fallen from a tree)

Non-Living Things
· Objects that are not alive or ever will be (Ex. Metal desk)

Plants
· Organisms that are able to make their own food by the process of photosynthesis

Animals
· Organisms that must rely on other organisms for food

Differences between Plants and Animals
Plants	Animals
Able to make their own food	Rely on others for food
Contain chlorophyll	Do not contain chlorophyll
Have limited movement	Able to move from place to place (locomotion)
Contain a cell wall	Have no cell walls
Cells look brick-like	Cells are round

Topic 2: A Close Look at Growth and Reproduction

Growth
· The characteristic of life that allows all organisms to get bigger, change and repair themselves.

Life Cycle
· The stage of development that an organism goes through in its life.
· Includes the process of reproduction, the pattern of growth and its adult life.

Different organisms have different patterns of development with lots of variation

Growth spurts in humans

· Boys between age 14 - 16
·Girls between ages 11-13

Animals that grow in starts and stops such as animals with exoskeletons.

· Skeletons surround their body (outside)
· Ex. Lobster, crayfish and insects

·When these organisms grow they "shed" their shell. They then grow a larger one.
· Growth occurs in a series of spurts, between the shedding of the old skeleton and the hardening of the new one.

Growth for Repair
· All organisms can repair their muscle, skin and bones.

Regeneration
· The process by which an organism grows new tissue or body parts to replace those that have been destroyed.

Animals
Invertebrates	Vertebrates
Animals without backbones	Animals with backbones
Can grow back lost parts (Ex. Legs, claws, tails)	Limited ability to regenerate lost parts
Ex. Starfish, planaria, earthworm, lobster, crab, crayfish	Ex. Salamanders can regenerate a lost tail

Reproduction
·The replacement of an old generation by a new generation.

·The process of producing a new generation.

Two Types of Reproduction
Asexual	Sexual
1. Amoeba (splitting in two)	1. Humans
2. Strawberry plants (runners)	2. Animals
3. Potatoes (eyes)	3. Plants (with both male and female parts)

Topic 4: A Close Look at Movement (pp. 34-45)

Locomotion
· Locomotion - The process of moving from place to place.

Types of Locomotion

1. Animals with legs and skeletons (Ex. Humans/grasshoppers)

· Skeletons - provide support

· Muscles - Attach to the bones they contract (shorten) creating a push or pull of the legs.
· Ex. Humans (Skeleton inside the body) or Grasshopper (Skeleton outside the body-exoskeleton)

2. Animals with No Legs
· Skeleton - provides support, bendable
· Muscles - expand and contract

· Ex. Snake - It slithers along the ground in S-shaped curves, pushing off rocks, grass, etc.

3. Animals with No Legs and No Skeleton
· Flexible bodies - divided into segments

· Segments - contain 4 pairs of bristles (giving grip)
·Two types of muscles - allow the work to make itself longer and shorter (together with the bristles allowing it to move forward)
· Ex. Earthworm

4. Movement in Water
·Move through the water by curving their bodies and wriggling back and forth
· Fins and tail help it move forward and in other directions.

· Ex. Fish, shark

Movement
· Movement - A change in an organisms shape or position (limited)

Internal Movement

·Movement inside the body (Ex. blood flow)

Vital signs

· Signs that show the body are functioning properly.
·Types: Body temperature, blood pressure, pulse and breathing rate

Movement in Plants
· Movement in plants is "less obvious" than movement in animals

Examples

1.Shoots

·Hedge plants send out shoot
· The plant spreads across the ground

2.Bending toward light

· Plants grow toward the Sun;more favorable conditions

3.Sensitivity
· Mimosa will lose water and sags when touched
· Venus flytrap closes its leaves when touched

Topic 5: Sensing and Responding to the Environment (pp. 46-51)

Stimulus
· Anything that causes an organism to react
·Ex. Bright light causes the pupils of the eye to dilate.

Response
· To react to a stimulus

Sense Organs

· Specific parts that detect stimuli and respond to it

· Ex. Eyes, ears, nose, skin, tongue

Reaction time
·The speed in which an organism responds.

Receptor

·A group of cells in a sense organ that receives a message from the outside world
· The body part that receives the stimuli.

Examples of Stimuli and Responses

1. A plant grows toward the light

· Stimulus - light

· Response - Movement (growth) toward the light

2. The teacher yells, the student moves away

· Stimulus - Yelling

· Response - Movement away

Positive response

· Movement towards the stimulus

Negative Response

· Movement away from the stimulus

Handling the Microscope (pp. 368-372)

Two Types of Microscope

1. Simple

· Contains one lens

2. Compound

· Contains two or more lenses

How to Handle a Microscope

· Use two (2) hands to carry; one on the base & one on the arm

·Place on a clean/level surface. Away from the edge.

· Check the plug before you start.

· Keep clean.

·Begin to focus using low power first.

·Cover after use.

Wet mount

· A glass slide that uses water and a cover slip.

· Prepared to use under the microscope.

Stain

· A chemical that is used to make parts stand out.

How to Prepare a Wet Mount Slide

1. Start with a clean slide.

2. Add a drop of water.

3. Place a sample in water.

4. Cover the slide with a slip; drop it at an angle of 45 degrees to avoid air bubbles.

5. View under a microscope.

How to Use a Microscope

1. Place a slide on the stage.

2. Start at LOW power; use fine & coarse adjustment.

3. Move to medium power; use only FINE adjustment knob.

4. Move to high power; use only FINE adjustment knob.

Parts of a Microscope and their Function

Part	Function
Eyepiece	Eye views object under observation
Coarse adjustment focusing knob	Dial used to make the object clearer in the eyepiece
Fine adjustment focusing knob	Similar to the coarse adjustment focusing knob but for greater clarification
Stage	Flat surface o the microscope used to mount slides upon
Base	Used to support the microscope on flat surface
Arm	Used to support the eyepiece, body tube and lens above the stage.
Lamp	Light source to improve viewing of slides
Diaphragm	Used to pinpoint light source on the slide

Cells

· The tiny, living building block, which makes up all living things.

Animal and Plant Cells
Similarities	Differences
Both plant and animal cells contain a nucleus, vacuoles, plasma membranes	Plant cells contain chloroplast Plant cells have larger food vacuoles Plant cells have cell walls Plant cells are rectangular; animal cells are round or oval

Cell Parts and their Functions
Part	Function
Nucleus	Control center of the cell (brain)
Vacuole	Stores the food
Cytoplasm	Jelly-like material (mostly water)
Plasma membrane	Allows material in and out of the cell
Chloroplast	Makes the food
Cell wall	Provides structure and support for the cell

Animal Cell Diagram

Plant Cell Diagram

posted by C. Fowler @ 9:47 AM