The main source of energy for MOST ecosystems on Earth is:

What is the process that AUTOTROPHS use to capture sunlight energy?

The Nature of SunlightSunlight strikes the Earth as a form ofelectromagnetic energy.

Electromagnetic energy takes the form ofa wave, with each type having a distinctwavelength.Wavelength: the distance between two adjacent crests in a wave series.

One Wave Length

The Electromagnetic SpectrumThe electromagnetic spectrum representsthe entire range of wavelengths of energy.

10-5 nanometers (gamma rays)

103 meters (radio waves)

(very short wavelength, high energy)

(very long wavelength, low energy)

The Segment of Light Important to Life on EarthVisible light has a wavelength range of 380to 750 nanometers.

Other wavelengths have an impact, but are not vital for photosynthesis.

Ex: Ultraviolet (UV) rays, Gamma rays, Infrared rays.

The Three Fates of LightVisible light that strikes an object can be:1)Reflected from the surface or internal structures of the object.2) Transmitted through the object.3) Absorbed by the object.

The colors that we can see are either reflected light or transmitted light.

The Three Fates of Light

Absorbance of LightSubstances that absorb visible light are called pigments.We see green plants because chlorophyll inthe plants absorb red and blue wavelengths,while reflecting green wavelengths.

Plant PigmentsThere are several pigments in plants, butonly a few are involved in photosynthesis.

The two pigments most involved with thecapture of sunlight energy are chlorophyll a and chlorophyll b. Another important type of pigments are the carotenoid pigments.

Pigments involved in photosynthesis are located on the thylakoid membranes of the chloroplasts.

Structure of Chlorophyll

Chlorophyll has a large ring assembly with a magnesium atomat its center.

A long hydrophobic tailanchors the pigment tothe chloroplast.

Chlorophyll Absorption SpectrumBoth Cha and Chb absorb wavelengths in the red and blue parts of the spectrum.

Carotenoids also absorb in the blue part of the spectrum, and may help absorb excess energy from light in those wavelengths.

The ABSORBTION SPECTRUM of PLANTS

Photosynthesis: How AUTOTROPHS gather energy.

Photosynthesis is an ENDOTHERMIC reaction, meaning it TAKES IN energy.

Where does it get the energy from?

In addition to needing sunlight, plants also need two chemicals for photosynthesis to work: Water, or H2O

Carbon Dioxide, or CO2

H2O and CO2 are called the REACTANTS

in Photosynthesis.

CO2 + H2O

C6H12O6 + O2C6H12O6 (Glucose) and O2 (Oxygen) are

the PRODUCTS of Photosynthesis

What does the plant use the Glucose for?

What does the plant use the Oxygen for?

Thomas Engelmann’s Experiment (1883)Illuminated long strands of filamentous algaewith different wavelengths, and used aerobic bacteria to show which segments were producing oxygen.