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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

The concept of mechanical advantage

The amount of effort saved when using machines is called mechanical advantage (MA). Simple machines use mechanical advantage as a key property to their functionality, helping humans perform tasks that would require more force than a person could produce. We will use the lever as an example of a simple machine to illustrate the concept of mechanical advantage.

Onderwerp en thema
Form 2
Physics
Simple machines
Concept of simple machines
Type bron
Werkbladen en klassikale activiteiten
Taal
English
Uitgever
Department of Higher Education
Publicatiedatum
No date
Schepper/Auteur
Leigh Kleynhans
Deelnemer
Michael Atkinson
Trefwoord
Effort Force
Resistance Force
Mechanical Advantage

Density

Outcomes:

  • Describe how the concept of density relates to an object's mass and volume.
  • Explain how objects of similar mass can have differing volume, and how objects of similar volume can have differing mass.
  • Explain why changing an object's mass or volume does not affect its density (ie, understand density as an intensive property).
  • Measure the volume of an object by observing the amount of fluid it displaces.
  • Identify an unknown material by calculating its density and comparing to a table of known densities.
Onderwerp en thema
Form 1
Biology
Introduction to biology
Scientific processes in biology
Type bron
Simulatie
Taal
English
Uitgever
pHET Interactive Simulations
Publicatiedatum
2023
Schepper/Auteur
Diana López Tavares
Jonathan Olson
Trefwoord
Density
Mass
Volume
Archimedes' Principle

Evolution Clarification Swahili

Clarifying some points on evolution and intelligent design.

Onderwerp en thema
Form 1
Biology
Introduction to biology
Scientific processes in biology
Type bron
Video
Taal
English
Uitgever
KhanAcademyKiswahili
Publicatiedatum
2012
Schepper/Auteur
Khan Academy
Deelnemer
KhanAcademyKiswahili
Trefwoord
Evolution
Human Evolution

Human fertilisation and early development

Overview of fertilisation and early human development. From conception leading to a zygote to blastocyst, embryo and fetus.

Onderwerp en thema
Form 1
Biology
Introduction to biology
Scientific processes in biology
Type bron
Video
Taal
English
Uitgever
Khan Academy
Publicatiedatum
2017
Schepper/Auteur
Sal Khan
Trefwoord
fertilisation

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

Mechanical advantage of simple machines

In this unit we will learn how these factors can affect the output of a simple machine. We will also learn about the difference between ideal mechanical advantage (IMA) and actual mechanical advantage (AMA), and how to apply your knowledge to calculate the efficiency of various simple machines.

Onderwerp en thema
Form 2
Physics
Simple machines
Concept of simple machines
Type bron
Studieboeken
Taal
English
Uitgever
Department of Higher Education
Publicatiedatum
No date
Schepper/Auteur
Leigh Kleynhans
Deelnemer
Michael Atkinson
Trefwoord
Lever
Inclined plane
Vectors
Effort Force

Mitosis

Mitosis is how cells divide! Learn what happens in all the phases of mitosis: prophase, metaphase, anaphase, and telophase.

Onderwerp en thema
Form 1
Biology
Introduction to biology
Scientific processes in biology
Type bron
Video
Taal
English
Uitgever
Khan Academy
Publicatiedatum
2015
Schepper/Auteur
Sal Khan
Trefwoord
Mitosis
Cells

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