7th grade science

7th Grade Science

http://www.bergoiata.org/fe/felins/10.htm

http://www.jonathanpmiller.com/intercalation/B-DNA.jpg

http://www.bergoiata.org/fe/felins/10.htm

© Fall 2005, Pflugerville ISD, 7th Grade Unit 2 : Chapter 7 : Section 1

It’s Alive!! Or, Is It?

What characteristics do all living things have in common?

What Do You Think?



There are Six Characteristics of Living Things.

1. Living things have Cells.

2. Living things Sense and Respond to Change.

3. Living things have DNA.

4. Living things Reproduce.

5. Living things use Energy.

6. Living things Grow and Develop.



• An object must possess all 6 of the characteristics in order for it to be considered a living thing.



1. Living Things Have Cells

• Every living thing is made up of one or more cells.

• Cells are the simplest collection of matter which has all the properties of life.

• Some cells specialize to do specific jobs.• Examples are nerve cells, muscle cells,

etc…



2. Living Things Sense and Respond to Change.

• A stimulus is a change that causes the activity of an organism to change.

• A stimulus can be internal (from inside).– Examples are fever or vomiting when sick.

• A stimulus can be external (from outside).– Example is squinting when the lights are

bright.



2. Living Things Sense and Respond to Change (cont…).

• Homeostasis is the maintenance of a stable internal environment.- Our bodies are very good at controlling the chemical reactions that keep us alive. These reactions can only take place when conditions are exactly right.- Even though our outside conditions may change, homeostasis keeps our internal conditions the same.- Example is body temperature.



3. Living Things Have DNA.

• DNA stands for deoxyribose nucleic acid.• DNA is the molecule that controls the

functions of a cell.• DNA is passed from parent to offspring.



4. Living Things Reproduce.

• Most living things reproduce by sexual reproduction.

• Sexual reproduction requires two parents that produce offspring that share characteristics of both parents.

• Sexual reproduction produces more diverse more diverse offspring.

Animals

http://www.jpbutler.com/thailand/images/elephant-and-baby.jpg



4. Living Things Reproduce (cont…).

• Some things reproduce by asexual reproduction.

• Asexual reproduction occurs when a single parent produces offspring that are exactly the same as the parent.

• This leads to more uniform offspring.

Hydra

http://universe-review.ca/I10-26-hydra.jpg



5. Living Things Use Energy• Metabolism is the total of all of the chemical

activities that the organisms performs.• Metabolism includes:

- Making food.

- Breaking down food.

- Building cells.

- Moving materials in and out of cells.http://www.faculty.ucr.edu/~insects/systems/metabolism/metabolism.gif



6. Living Things Grow and Develop.

• You grow as your body gets bigger.• Developing is the process of changing,

maturing, and going through different stages.

• Growing and developing depends on the environment and the resources available.


It’s Alive!! Or, Is It?Tr

y Th

is! Visit the website below to distinguish between Living

and Non-living things.

Ready?

Living and Non-living things


Let’s Review!

- 1 -

If the weather is cold outside, how do you maintain your

body temperature?


Answer

• If it’s too cold, you will shiver to create heat. Humans can add layers of clothes to keep warm in the cold. Reptiles bask in the sun to stay warm. Homeostasis allows us to do this.

http://www.utexas.edu/opa/news/02newsreleases/nr_200205/graphics/turtle2.jpg


Let’s Review

- 2 -

• What characteristics of living things does a river have?

• Is a river alive?


Answer

• A river has energy (it moves) and can grow larger (after rain), but it is not alive because it is not made of cells, cannot respond to stimuli, has no DNA, and cannot reproduce.



Websites to Visit

• Cells Alive

• Prokaryotes and Eukaryotes



What are several thing that are necessary for living things to

survive?

What Do You Think?



• Food

• Water

• Air

• A place to live


The Cell in Action

Make a Venn diagram comparing and contrasting photosynthesis and cellular respiration.

Activity


Let’s Review!

- 1 -

Why are producers (who use photosynthesis) important to

the survival of all other organisms?


Answer

• Producers harness energy in sunlight to produce food (glucose). This food becomes an energy source for producers and for the organisms that consume them.

© Fall 2005, Pflugerville ISD, 7th Grade Unit 2 : Chapter 8

The Cell in Action

Websites to Visit

Good Diffusion Labs!

Transport In and Out of Cells

Photosynthesis

Cellular Respiration

© Fall 2005, Pflugerville ISD, 7th Grade Unit 2 : Chapter 8 : Pre-AP

The Cell in Action

Pre-AP Extensions for Chapter 8

There are 2 types of endocytosis. Each process bring particles into the cell.

1. Pinocytosis

2. Phagocytosis


The Cell in Action


1. Pinocytosis involves ingesting small molecules and/or fluids surrounding the cell.

• The cell membrane surrounds and “pinches off” small droplets and places them in a vesicle inside the cell.

• Most of the molecules are already dissolved in a solution during pinocytosis.


The Cell in Action


Pinocytosis

http://www.cat.cc.md.us/courses/bio141/lecguide/unit2/eustruct/pinocyt.html

•The small molecules are ingested by the cell membrane and used inside the cell.


The Cell in Action


The second type of endocytosis is called phagocytosis.

• Phagocytosis is the process of surrounding, engulfing, and digesting larger, microscopically visible particles.

• Phagocytosis is used by most protozoans to get food.

http://www.oum.ox.ac.uk/children/animals/protists.gif


The Cell in Action


http://academic.brooklyn.cuny.edu/biology/bio4fv/page/phago.htm

Phagocytosis•In phagocytosis, the food particle is too big to “absorb” through the cell membrane. It must be surrounded and engulfed.

7th grade science

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