• electromagnetic radiation.
• visible part of the spectrum.
• Important for photoperiodism.
• A predictable cue, not like temperature.
• Important in carbon fixation.

• Occurs in chloroplast of green plants/algae.
• Enzymes necessary.
• Light energy required.

• Occurs in mitochondria.
• Enzymes necessary.
• ATP and heat energy released.

1. Light is absorbed by chlorophyll A& B.
2. e- is raised to a higher energy level.
3. H2O is split.
4. O2 is released.
5. ATP is produced.
6. NADPH2 (NADPH,H+) is produced.

• Net results - energy is changed from electromagnetic radiation to chemical energy.
• Type of energy cannot be stored long.
• Reactions require electromagnetic radiation.
• Same reaction in all plants.

1. CO2 is fixed.
2. ATP is used up.
3. NADPH2 is used up.
4. A hexose sugar is produced.
5. RuBP (RuDP), and sometimes PEP are regenerated.

• Light is not required. Can go on in light or dark.
• Three different path ways: C3, C4, CAM.

• ribulose biphosphate (5C) (RuDP –ribulose diphosphate (5C))
• requires high levels of CO2.
• can use CO2 or O2 as a substrate.
• has photorespiration.

• phosphoenolpyruvate (3C).
• does not require high levels of CO2.
• does not use O2 as a substrate.
• no photorespiration

Occurs in mesophyll cells. Only RuBP carboxylase.

[image]

• Stomates closed during the day.
• CO2 fixed at night.
• Better adapted to hot-dry condition.

• No photorespiration.
• PEP carboxylase works at low CO2 concentration.
• Location of PEP & RuBP carboxylase in leaf tissue.

• Photorespiration is a reaction where RuBP is broken down in the presence of O2.
• Rather than a hexose sugar being produced, the RuBP is broken down, and energy is lost.
• It is a competitive reaction with the fixing of the CO2.
• Whichever gas, CO2 or O2 is predominant, will determine which reaction (carbon fixation or photorespiration) will occur.

• a chemical which inhibits the production of malic acid.
• C3 - Addition of malonate has no effect on hexose sugar production.
• C4 - Malic acid is an intermediate of photosynthesis.
• Addition of malonate reduces hexose sugar production.
• CAM – Malic acid is a temporal intermediate for photosynthesis
• day - malic acid is broken down; ↑ pH.
• night - malic acid is a product; ↓ pH

• environment.
•  # of young produced.
• survival of young.
• length of reproductive period.

• Exponential growth
• Logistic growth

• under ideal conditions.
• growth is at its maximum, limited only by reproductive physiology of the species; cannot occur indefinitely

Formula for change in population:

[image]

r= rate of growth

N= initial population

• growth is limited by the maximum number of individuals the environment can sustain
• (K: carrying capacity)
• the greater the size of the population the greater the dampening effect of K on the growth of the population

[image]

• Lack of nutrients.
• Starvation.
• Disease.
• Emigration.
• Competition.
• Habitat alterations

predator-pray interactions

Models

Lotka-Volterra Model (graph two sine waves)

• Assumtions of the Model
• Constant food supply for prey
• predator food supply depends entirely on pray population
• no threat to the prey other than the specific predator (exponential growth withour predation)
• No: disease, climate change, other predators

1. Primary sucession- takes place in new habitats
• Bare rock
• Volcanic ash
• lava flows
• new sand dunes
2. Secondary sucession - other species or communities have proceeded 
• Old fires
• Disturbed areas (floods, fire etc.)

1. Allogenic (Abiotic) caused by external geophysiochemical forces
• pond filling with sedement
2. Autogenic (Biotic) caused by internal biotic forces 
• grass effects on soil: ↓light ↓evaporation ↑soil moisture↑nutrients

1. Xerarch- dry or desert
2. Xerosere: sere that occurs under dry conditions
• Lithosere: surface of rock
• Psammosere: originates in sand/dandy soils
3. Mesarch- wer, but terrestrial (river bank)
4. Hydrarch - acquatic

species change the abiotic environment.

early species prepare the way for later species

EX: huisache

1.species can invade new habitat and become established independently of the presence or absence of other species

2. the life spans and competitive abilities of a species determines its position and dominance within the sere

3.juveniles of climax species can be present in earliest stages

1.species resist invasion of competitors; early arrivals inhibit colonization by later arrivals - may involve toxins

2.later successional species can only invade if space is opened up by disturbance or death of early colonists

the ratio of major resources change through time and species respond to the changes (Light and Nitrogen)

[image]

1. changes in resources
1. (light ↓, NH3, N-fixation)
• productivity ↑
• biomass ↑
•  # of species highest during transition
2. changes in species (pines and hardwoods) 
3. animal trends

influenced by common species.

min value 1.

probability that two species will be the same.

[image]

influenced by rare species.

min value 0.

predicts the next species.

[image]