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BIOB11H3 Study Guide - Final Guide: Photorespiration, Xylem, Bioremediation

Biological Sciences
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Chapter 5
Discovery that crows use food-gathering tools was quite surprising because originally
thought that only primates used tools
oTwo types of tools: hooked twig stripped of leaves and bark and serrated edge
clipped off a tree
oThis tools were manufactured by the birds
oThey also appeared uniform in construction
The consistency in construction of the tools indicate a cultural phenomenon i.e. the skill
of tool-making is learned socially within a population of birds
Energy is most basic requirement of all organisms and everything dies without it
Radiant energy: light from the sun
Kinetic energy: energy associated with the motion of molecules that make up objects i.e.
touching a cold object is experiencing kinetic energy
Chemical energy: stored in food that is being consumed
Radiant and chemical energy are what organisms use to meet demands of growth and
maintenance while kinetic energy is important for controlling rate of activity and
metabolic energy demand of organisms
Autotrophs: organisms that assimilate energy from sunlight or from inorganic
compounds in their environment
oConvert this energy into chemical energy stored in the carbon bonds of organic
compounds for consumption
Heterotrophs: organism that obtain their energy by consuming energy-rich organic
compounds made by other organisms
oIncludes detritovores (feed on dead things), parasites, herbivores and predators
Some plants have lost their photosynthetic function and obtain their energy by
parasitizing other plants (holoparasites) ex. Dodder
Hemiparasites are photosynthetic but obtain some of their energy from host plants
Animals can act as autotrophs but usually quite rare
oPhotosynthetic capabilities acquired by consuming photosynthetic organisms or
by living in symbiosis ex. sea slugs
Vast majority of autotrophic production occurs through photosynthesis while a little is
contributed by chemosynthesis, process that uses energy from inorganic compounds to
produce carbohydrates
Chemosynthesis harvest energy from inorganic compounds
Earliest autotrophs were probably chemosynthetic bacteria or archaea
During chemosynthesis, organisms obtain electrons from the inorganic substrate and use
the electrons to generate ATP and NADPH
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oUse energy from these molecules for uptake of carbon from gaseous CO2
(fixation of CO2)
oUse that carbon to synthesize carbohydrates which are then used for energy
Some bacteria can use electrons from inorganic substrate directly to fix carbon
The biochemical pathway most commonly used to fix carbon is Calvin cycle
oOccurs in both photosynthetic and chemosynthetic organisms
Most widespread and important chemosynthetic organisms are nitrifying bacteria, found
in aquatic and terrestrial ecosystems
oConvert ammonium in nitrite and then oxidize it to nitrate
oImportant for nitrogen cycling and plant nutrition
Another important chemosynthetic group is sulfur bacteria
oOriginally use higher-energy form of sulfur producing elemental sulfur but once
that runs out, use elemental sulfur and produce sulfate
Table 5.1: Inorganic substrates used by chemosynthetic bacteria as electron donors for
carbon fixation
Substrate Type of Bacteria
Ammonium Nitrifying bacteria
Nitrite Nitrifying bacteria
Hydrogen sulfide Sulfur bacteria
Sulfur Sulfur bacteria
Ferrous iron Iron bacteria
Hydrogen Hydrogen bacteria
Phosphite Phosphite bacteria
Photosynthesis is the powerhouse for life on Earth
Van Helmont established basis for later discovery that it was photosynthetic uptake of
CO2 from the air that was source of a trees weight gain during development
Leaves are principal photosynthetic tissue in plants but photosynthesis may also occur in
stem and reproductive tissues
Photosynthesis also responsible for largest movements of CO2 between Earth and
atmosphere which is critical for climate system
First step of photosynthesis is harvesting of energy from sunlight which is used to split
water to provide electrons for generating ATP and NADPH (light reaction)
Second step is fixation of carbon and synthesis of carbon (dark reaction)
Chlorophyll gives photosynthetic organisms their green appearance because it only
absorbs red and blue light, reflecting green wavelengths
oPigment involved in photosynthesis
Accessory pigments include carotenoids (red, yellow in appearance)
Photosynthetic pigments are embedded in chloroplasts which absorb energy from
photons of sunlight
oEnergy used to split water and provide electrons
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