IB BIO unit 2 day 1 & 2 cell orgin, stem cells(and microscopes)

DOGRACER-Characteristics of living things

DNA, Organization, Growth (getting bigger), Reproduction, Adapt, Cells, Energy, Respond

Francesco Redi - 1668 experiment

tested the theory of spontaneous generation (the idea that living things can arise from non-living matter) by using rotting meat in jars.

Louis Pasteur - 1862

swan-necked flask experiment

3 parts of the cell theory

1. All living things are made of cells.

   1. Unicellular or multicellular

2. Cells are the smallest unit of life.
   
   

3. Cells can only come from existing 

cells.

Unusual cells examples

Muscle cells, algae cells, fungus

The Miller-Urey Experiment overview

Found that early earth atmosphere + energy (electrical spark) = amino acids!

The Miller-Urey Experiment - 1953

Stanley Miller and Harold Urey set up an experiment to see if organic molecules could form from the gases in early Earth's atmosphere. They filled a glass setup with methane, ammonia, hydrogen, and water, and then shot electrical sparks through the gas mix to simulate lightning. Within a week, they saw that simple organic molecules formed, including many amino acids. This experiment provided evidence supporting the theory that lightning and UV radiation likely supplied the energy for chemical reactions on ancient Earth.

What were four of the potential problems with the Urey Miller experiment?

1.Was the atmosphere really ammonia, methane, water vapor, and carbon dioxide?

2.Did silicates in the glass take part in the reactions, and were they present on Earth?

3.Could the energy have come from UV rather than lighting?

4.They didn’t include any elements from rocks on the Earth which may have reacted too.

Last Universal Common Ancestor: LUCA

• The cell(s) that all life evolved from

• Based on DNA and RNA evidence

• Likely not one cell

What are two sources of evidence for LUCA?

universal genetic code and shared genes across organisms

What are two approaches used to date the origin of the first cells?

fossil dating and molecular clock evidence

What is the RNA world hypothesis?

The RNA world hypothesis says that early life shared RNA molecules that could store genetic instructions like DNA and speed up chemical reactions like proteins.

Explain why multicellular organisms exist instead of organisms consisting of one giant cell. Why can cells only grow to a certain size?

Cells can only grow to a certain size because as they get bigger, their volume grows faster than their plasma membrane, which makes it too hard to bring food and get rid of waste.

Multicellular organisms exist so living things can grow larger by having many small cells working together instead of one big cell.

Microscopes two types

Compound and Dissecting

Electron Microscopes

• Use electromagnets to focus electrons resulting in greater magnifications and resolutions

• Can be used to view dead specimens in monochrome but color rendering may be applied

Two types of electron microscopes

Scanning electron and Transmission electron microscopes

Transmission electron microscopes (TEM)

• Pass electrons through specimen to generate a cross-section

Shoots electrons straight through a sample to show the inside (a cross-section).

Scanning electron microscopes (SEM)

• Scatter electrons over a surface to differentiate depth and map in 3D

Scatters electrons over the outside of something to make a 3D map.

Magnification steps

• Measure object with ruler (mm)

• Measure the scale bar with ruler (mm)

• Calculate how many scale bar lengths make the specimen

• Multiply the scale bar label by the number of lengthsMeasurement Conversions

Measurement Conversions

• 1 m (meter) = 1000 mm (millimeters)

• 1 mm (millimeter) = 1000 𝝁m (micrometers)     

• 1  𝝁m (micrometer) = 1000 nm (nanometers)

Stem Cells

• Early in development, our cells are still unspecialized

• They differentiate through development as they divide

How do cells differentiate?

Differentiation is the process of expressing some genes in some cells but not in others 

Euchromatin

less condensed DNA = high expression

Heterochromatin

more condensed DNA = low expression

Types of Stem Cells

• Totipotent: can differentiate into any cell type 

• Pluripotent: many cell types

• Multipotent: few closely related cell types

• Unipotent: only into associated cell type

How are stem cells used?

• Replacing damaged tissue with YOUR OWN new tissue

  • Retinal cells

  • Skin cells

  • Nerve cells

  • Blood cells