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 CO 2 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 C 3 Photosynthesis –Used by most plants and algae. –CO 2 enters leaves BUT water vapor leaves Poorly adapted to hot dry environments C 4 /CAM photosynthesis: Modifications in biochemical processes – Increased efficiency in CO 2 absorption –Fewer stomata required/stomata only open during night  decreased loss of water vapor

C 3 Photosynthesis CO2 enters passively so stomata have to be open for long periods of time

Why C3 Photosynthesis Doesn’t always work out - CO 2 must enter though stomata stomata (sing., stoma) are tiny holes on the undersides of leaves CO 2 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

C 4 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

ProducersHerbivores –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 TTER/Index.htmhttp://itech.pjc.edu/sctag/E_O TTER/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