Download - Energy and Living Things
Energy and Living Things
Outline• Energy Sources• Solar-Powered Biosphere• Photosynthetic Pathways• Using Organic Molecules• Chemical Composition and Nutrient
Requirements• Using Inorganic Molecules• Energy Limitation• Food Density and Animal Functional
Response• Optimal Foraging Theory
Energy Flows Through Living Systems
Plants= Autotrophs
Heterotrophs
• Autotroph: ‘self feeder’ - an organism that can gather energy (usually from light) … to store in organic molecules– Photosynthesis– chemosynthesis
• Heterotroph: An organism that must rely on other organisms to capture light energy … must rely on breakdown of organic molecules produced by an autotroph as an energy source– Classified by trophic level
Photosynthesis • Capture and transfer light energy to chemical
bonds• Occurs in:
– Plants– Algae– Certain Bacteria
• Not a perfect process – some energy is lost - entropy
How Photosynthesis Works• Light strikes leaf• Energy absorbed by chemical pigments• Absorbed energy drives chemical
processes to convert CO2 into larger molecules– First simple sugars – 6 carbon ring structures– Later many molecules of simple sugars joined
together to form larger molecules or converted to other compounds
– Energy absorbed in building larger molecules, released as they are broken down
Only certain Wavelengths of Light are Used in Photosynthesis
• Light Energy Used = ‘Photosynthetically Active Radiation’ or PAR – How Much is absorbed: determined as photon flux
density.• Number of photons striking square meter surface each
second.
• Chlorophyll absorbs light as photons.• Landscapes, water, and organisms can all change the
amount and quality of light reaching an area.
• Light not absorbed is reflected– Some in PAR + all in green and yellow wavelengths
Absorption spectra of chlorophylls and carotenoids
Wavelengths most useful in driving photosynthesis
Wavelengths not used - reflected
Fall color• In many
plants production of chlorophyll ceases with cooler temperatures and decreasing light
• other pigments become visible
Modifications of Photosynthesis for Dry Climates
• C3 Photosynthesis
– Used by most plants and algae.
– CO2 enters leaves BUT water vapor leaves• Poorly adapted to hot dry environments
• C4/CAM photosynthesis: Modifications in biochemical processes– Increased efficiency in CO2 absorption
– Fewer stomata required/stomata only open during night decreased loss of water vapor
C3 PhotosynthesisCO2 enters passively so stomata have to be open for long periods
of time
Why C3 Photosynthesis Doesn’t always work out -
CO2 must enter though stomata• stomata (sing., stoma)
are tiny holes on the undersides of leaves
• CO2 enters and moisture is released
• In hot, dry climates, this moisture loss is a problem
C3 grasses (yellow)
dominant in cool temperate
– C4 plants don’t compete so well there
C4 grasslands (orange) have evolved in the tropics
and warm temperate regions
C4 Photosynthesis
Photosynthetic Pathways
• CAM Photosynthesis– (Crassulacean Acid Metabolism)– Limited to succulent plants in arid and semi-
arid environments.• Carbon fixation takes place at night.
– Reduced water loss.
• Low rates of photosynthesis.• Extremely high rates of water use efficiency.
CAM Photosynthesis
• Producers • Herbivores– Animals that eat plants– The primary consumers
of ecosystems
– Green plants and algae– Use solar energy to build
energy-rich carbohydrates
• Carnivores
– Organisms that eat dead organisms
• Decomposers– Organisms that
break down organic substances
– Animals that eat herbivores– The secondary consumers of ecosystems– Omnivores are animals that eat both plants and animals– Tertiary consumers are animals that eat other carnivores
• Detritivores
Efficient Breakdown of Products of Photosynthesis Requires Oxygen
• Complex series of reactions, oxygen serves as the terminal electron acceptor
• May occur in some organisms w/o oxygen (anoxic conditions)– anaerobic respiration= fermentation– Inefficient– End products vary with organism involved
• Ethanol, proprionic acid, lactic acid, etc.
• Three Feeding Methods of Heterotrophs:– Herbivores: Feed on plants.– Carnivores: Feed on animal flesh.– Detritivores: Feed on non-living organic matter.
Classes of Herbivores
• Grazers – leafy material
• Browsers – woody material
• Granivores – seed
• Frugivores – fruit
• Others – nectar and sap feeders– Humming birds, moths, aphids, sap suckers
…
Herbivores
• Substantial nutritional chemistry problems.– Low nitrogen concentrations – difficulty
extracting needed protein/amino acids from source.
– Require 20 amino acids to make proteins ~ 14 are must come from diet
How do plants respond to feeding pressures by herbivores?
• Mechanical defenses – spines• Chemical defenses
– Digestion disrupting chemicals – tannins, silica, oxalic acid
– Toxins – alkaloids• More common in tropical species
How do animals respond?– Detoxify– Excrete– Chemical conversions – use as nutrient
• Digestion Schemes of Herbivores
• Require extensive digestive processing
• Rumnants – 4 part stomach– Rapid feeding,
coarse material is re-milled (regurgitated bolus) after initial fermentation
• ‘Chewing their cud’
• Coprophagy: expel moist fecal material, re-ingest– 50-80% of fecal
material recycled • acts as external
rumen • bacterial activity
produces B vitamin Cecum is site of
much bacterial activity, moist fecal pellets enclosed in
protein produced
Carnivores
• Predators must catch and subdue prey - size selection.– Usually eliminate more conspicuous members
of a population (less adaptive).– act as selective agents for prey species.
• European River Otter:• Lutra lutra• Widest ranging of
otters• Diet varies with
abundance of prey
• http://itech.pjc.edu/sctag/E_OTTER/Index.htm
Optimal Foraging Theory
• Assures if energy supplies are limited, organisms cannot simultaneously maximize all life functions.– Must compromise between competing
demands for resources.• Principle of Allocation
• Fittest individuals survive based on ability to meet requirements principle of allocation
Optimal Foraging Theory
• All other things being equal,more abundant prey yields larger energy return. Must consider energy expended during:
• Search for prey• Handling time
• Tend to maximize rate of energy intake.
• What would a starving man do at an all you can eat buffet?
Optimal Foraging in Bluegill Sunfish
Adaptations of Prey to being preyed upon
• Predator and prey species are engaged in a co-evolutionary race.
• Avoid being eaten – avoid starving/becoming extinct
• Defenses:– Run fast– Be toxic – and make it known– Pretend to be toxic
• Predators learn to avoid
Carnivores• Consume nutritionally-rich prey.
– Cannot choose prey at will.• Prey Defenses:
– Aposomatic Coloring - Warning colors.– Mullerian mimicry: Comimicry among several species of
noxious organisms.– Batesian mimicry: Harmless species mimic noxious species.
Mullerian mimicry: Comimicry
Batesian mimicry: Harmless species mimic noxious species
Aposomatic Coloring - Warning colors
Detritivores
• Consume food rich in carbon and energy, but poor in nitrogen.– Dead leaves may have half nitrogen content
of living leaves.
• Fresh detritus may still have considerable chemical defenses present.
Detritivores and decomposers
Review• Energy Sources• Solar-Powered Biosphere• Photosynthetic Pathways• Using Organic Molecules• Chemical Composition and Nutrient Requirements• Using Inorganic Molecules• Energy Limitation• Food Density and Animal Functional Response• Optimal Foraging Theory• Adaptations