Energy and Living Things Outline Energy Sources SolarPowered

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 Heterotrophs Plants= Autotrophs

• 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

Law of the minimum- ecosystems must adapt to it. • • Light in ocean floor Water in desert Heat on mountain top Matter is also limiting, thus have limiting nutrients that allow for life

Flow of energy and nutrients • Photosynthesis • Metabolism

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 – 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: Number of light energy (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

Wavelengths most useful in driving photosynthesis Absorption spectra of chlorophylls and carotenoids Wavelengths not used - reflected

Fall color • In many plants production of chlorophyll ceases with cooler temperatures and decreasing light • other pigments become visible

C 3 Photosynthesis CO 2 enters passively so stomata have to be open for long periods of time

Why C 3 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

• Producers Food Web • Herbivores – Green plants and algae – Use solar energy to build energy-rich carbohydrates – Animals that eat plants – The primary consumers of ecosystems • Carnivores – – 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 – Organisms that eat dead organisms • Decomposers – Organisms that break down organic substances

Thermodynamics v Total amount of energy kept constant v Energy can be converted

Transfer of Energy with Ecosystems • Board notes

• 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

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.

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

productivity • Refers to the production of food • Primary production = total gross primary production • Activity- Compare ecosystems p. 26

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

Cycles of matter • Nitrogen • Carbon

Nutrient Cycling and Retention Chapter 19

Nitrogen Cycle • Includes major atmospheric pool - N 2. – Only nitrogen fixers can use atmospheric supply directly. • Energy-demanding process. – N 2 reduced to ammonia (NH 3). • Once N is fixed it is available to organisms. – Upon death of an organism, N can be released by fungi and bacteria during decomposition.

Nitrogen fixation Biological Nitrogen Fixation (BNF) occurs when atmospheric nitrogen is converted to ammonia by a pair of bacterial enzymes n. N 2 + 8 H+ + 8 e− + 16 ATP → 2 NH 3 + H 2 + 16 ADP + 16 Pi

Microbes Denitrification NO 3(nitrate) → NO 2 - → NO → N 2 gas Nitrogen Cycle

Carbon Cycle • Moves between organisms and atmosphere as a consequence of photosynthesis and respiration. – In aquatic ecosystems, CO 2 must first dissolve into water before being used by primary producers. – Although some C cycles rapidly, some remains sequestered in unavailable forms for long periods of time.

Carbon Cycle

Animals and Nutrient Cycling in Terrestrial Ecosystems • Huntley and Inouye found pocket gophers altered N cycle by bringing N-poor subsoil to the surface. • Mac. Naughton found a positive relationship between grazing intensity and rate of turnover in plant biomass in Serengeti Plain. – Without grazing, nutrient cycling occurs more slowly through decomposition and feeding of small herbivores.

Animals and Nutrient Cycling in Terrestrial Ecosystems

Plants and Ecosystem Nutrient Dynamics • Fynbos is a temperate shrub/woodland known for high plant diversity and low soil fertility. – Two species of Acacia used to stabilize shifting sand dunes. • Witkowski compared nutrient dynamics under canopy of native shrub and introduced acacia. – Amount of litter was similar, but nutrient content was significantly different. – Acacia - N fixer

Biotic communities

Climate and weather