introduction to cells wheel

8/3/2019 Introduction to Cells WHEEL

1/16


2/16

Zacharias Jansen1595 He was known as "street seller" who was constantly in

trouble with the local authorities.

Invented the first microscope.


3/16

Anton van Leewenhoek1668 Came from a family of tradesmen, had no fortune,

received no higher education or university degrees.

Succeeded in making some of the most importantdiscoveries in the history of biology. Discovered bacteria, free-living and parasitic microscopic

protists, sperm cells, blood cells, microscopic nematodes androtifers, and much more.

His research opened up an entire world of microscopiclife to the awareness of scientists.


4/16

Leeuwenhoek is known to have made over 500"microscopes," of which fewer than ten have survivedto the present day.

Early compound microscopes were not practical formagnifying objects more than about twenty or thirtytimes natural size; Leeuwenhoek built microscopesthat magnified over 200 times, with clearer andbrighter images than any of his colleagues couldachieve.


5/16

Leewenhoeks Microscope


6/16

Robert Hooke1678 Relatively little is known

about Robert Hooke's life. Was educated at home by

his father, enteredWestminster School at theage of thirteen, and fromthere went to Oxford,

where some of the bestscientists in England were

working at the time. Devised the compound

microscope, one of thebest microscopes of histime.


7/16

His most famous microscopic observation was of thinslices of cork.

. . . I could exceedingly plainly perceive it to be all

perforated and porous, much like a Honey-comb, butthat the pores of it were not regular. . . . these pores, orcells, . . .

Hooke had discovered plant cells -- more precisely, he

saw the cell walls in cork tissue. Hooke coined the term "cells": the boxlike cells of cork

reminded him of the cells of a monastery.


8/16

Thin slices of corkplant cells!


9/16

Matthias Schleiden--1838 German botaniststudied plants.

Stated that all plants are composed of cells.


10/16

Theodore Schwann1839 German physiologist.

Stated that all animals are composed of cells.


11/16

Rudolph Virchow1855

Stated that every cell originated from a preexistingcell.


12/16

Cell Theory (Schleiden, Schwann, Virchow)

1. All living organisms are composed

of cells. They may be unicellularor multicellular.

2. The cell is the basic unit of life.

3. Cells arise from pre-existing cells.


13/16

Most cell are microscopic, ranging from about 1-100micrometers in size.

Why are cells so small and why do large organismsconsist of many cells rather than one large cell?1. To quickly get the information inside the cell.

2. To ensure the information is accurate.


14/16

Does it take longer to get from the plasma membraneto the center of the cell in a small cell or a large cell? Large cell

Is it more efficient to take less time or more time topass on information? Less time


15/16

The greater the surface area, the more rapidlysubstances can be exchange with the environment.

When a cell increases in size, its volume increasesmore rapidly than its surface area. Very large cell would exchange materials too slowly to

survive.

Many small cells can have the same total volume as onelarge cell but still enough surface area for rapid changes.


16/16

One large cell Many small cells

Example: whole package ofcookie dough

Example: individual cookies

introduction to cells wheel

Documents