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Cell theory

Introduction to cell theory--the idea that 1) all living things are made of one or more cells, 2) cells are the basic unit of life and 3) all cells come from other cells. Explore the roles that Hooke, Leeuwenhoek and others played in developing cell theory.

Hooke and Leeuwenhoek were two of the first scientists to use microscopes to study the microscopic world of cells. Hooke coined the term "cell" after observing the tiny compartments in cork, while Leeuwenhoek discovered a variety of living creatures in pond water, blood, and other samples. They contributed to the cell theory by suggesting that cells are the fundamental units of life and structure, and that all living things consist of one or more cells that originate from other cells by division. 

Onderwerp en thema
Form 1
Biology
Cell structure and organisation
Concept of cells
Type bron
Video
Taal
English
Uitgever
Khan Academy
Publicatiedatum
2015
Schepper/Auteur
Sal Khan
Trefwoord
Cells

Cells and organisms

All living things are made up of cells, which is the smallest unit that can be said to be alive. An organism may consist of one single cell (unicellular) or many different numbers and types of cells (multicellular).

Onderwerp en thema
Form 1
Biology
Cell structure and organisation
Concept of cells
Type bron
Video
Taal
English
Uitgever
Khan Academy
Publicatiedatum
2022
Schepper/Auteur
Khan Academy
Trefwoord
Cells

Introduction to the cell

Introduction to the cell.

Onderwerp en thema
Form 1
Biology
Cell structure and organisation
Concept of cells
Type bron
Video
Taal
English
Uitgever
Khan Academy
Publicatiedatum
2017
Schepper/Auteur
Sal Khan
Trefwoord
Cells

Matter and energy in food webs

Food webs are models that demonstrate how matter and energy is transferred between producers, consumers, and decomposers as the three groups interact within an ecosystem. Transfers of matter into and out of the physical environment occur at every level. Decomposers recycle nutrients from dead plant or animal matter back to the soil in terrestrial environments or to the water in aquatic environments. The atoms that make up the organisms in an ecosystem are cycled repeatedly between the living and nonliving parts of the ecosystem.

Onderwerp en thema
Form 2
Biology
Balance of nature
Food chain and food web
Type bron
Video
Taal
English
Uitgever
Khan Academy
Publicatiedatum
2022
Schepper/Auteur
Sal Khan
Trefwoord
Food webs

Scale of cells

Even though molecules, proteins, viruses, and cells are all tiny, there are significant size differences between them. The diameter of a water molecule is roughly 0.28 nanometers. The diameter of the protein hemoglobin is roughly 5 nanometers. The diameter of the HIV virus is roughly 120 nanometers. A red blood cell is 6-8 micrometers.

Onderwerp en thema
Form 1
Biology
Cell structure and organisation
Concept of cells
Type bron
Video
Taal
English
Uitgever
Khan Academy
Publicatiedatum
2015
Schepper/Auteur
Sal Khan
Trefwoord
Cells

Visualising vectors in 2 dimensions

Visualising, adding and breaking down vectors in 2 dimensions.

Onderwerp en thema
Form 1
Physics
Force
Effects of forces
Type bron
Video
Taal
English
Uitgever
Khan Academy
Publicatiedatum
2011
Schepper/Auteur
Sal Khan
Trefwoord
Vectors
two dimensional motion

What is a force?

In this unit you will learn what a force is and find out about different types of forces. This will allow you to identify forces at work in your everyday life and understand the effects of forces.

Onderwerp en thema
Form 1
Physics
Force
Effects of forces
Type bron
Studieboeken
Taal
English
Uitgever
Department of Higher Education
Publicatiedatum
No date
Schepper/Auteur
Linda Pretorius
Deelnemer
Michael Atkinson
Trefwoord
Force
External Force
Net Force

Worked example: analysing a generic food web

We can analyse the arrows in a food web to identify producers, primary consumers, secondary consumers, and decomposers.

Onderwerp en thema
Form 2
Biology
Balance of nature
Food chain and food web
Type bron
Video
Taal
English
Uitgever
Khan Academy
Publicatiedatum
2022
Schepper/Auteur
Sal Khan
Trefwoord
Food webs

Worked example: analysing an ocean food web

We can analyse the arrows in a food web to identify producers, primary consumers, secondary consumers, and decomposers.

Onderwerp en thema
Form 2
Biology
Balance of nature
Food chain and food web
Type bron
Video
Taal
English
Uitgever
Khan Academy
Publicatiedatum
2022
Schepper/Auteur
Sal Khan
Trefwoord
Food webs