Coping with Environmental Variation:Energy

K. Harms photo

Use radiant energy from sunlight to produce molecules rich in chemical energy (carbon-carbon bonds;

consequently, C is often used as a measure of energy)

Autotrophs: Photosynthetic

6 CO2 + 6 H2O C6H12O6 + 6 O2

K. Harms photo

Green sea slug whose chloroplasts were usurped from its prey

Autotrophs: Photosynthetic

Cain, Bowman & Hacker (2014), Fig. 5.4

Autotrophs: Photosynthetic

Cain, Bowman & Hacker (2014), Fig. 5.6

Light-dependent (or light-driven) reactionsPigments harvest energy from sunlight to split water to provide electrons

to generate ATP & NADPH

Autotrophs: Photosynthetic

Light response curve from Cain, Bowman & Hacker (2014), Fig. 5.7 A

Light-independent (or carbon) reactionsEnergy from ATP & NADPH is used in the Calvin cycle for

carbon fixation (from CO2)

Autotrophs: Photosynthetic

Light response curves from Björkman’s (1981) experiments from Cain, Bowman & Hacker (2014), Fig. 5.7 B

Acclimatization of plants grown at different light levels

Autotrophs: Photosynthetic

Stomate of a tomato leaf from Wikimedia Commons

Water availability can influence PSNStomatal control trades off water conservation vs. energy gain

Autotrophs: Photosynthetic

Image from http://crescentok.com/staff/jaskew/ISR/botzo/class7.htm

Temperature can influence PSN

Autotrophs: Photosynthetic

Photo of delayed greening from https://www.flickr.com/photos/29289211@N05/4176185112/

Nutrient concentrations can influence PSNRubisco, a key enzyme associated with the Calvin cycle &

the most abundant enzyme on Earth, and other PSN enzymes are N-rich

Cellular Respiration

Image from Wikimedia Commons

Cellular respiration occurs in nearly all cells (microbe, plant, fungus, animal)Uses organic molecules to produce ATP

Aerobic respiration requires oxygen & employs the Krebs cycleAnaerobic respiration is poisoned by oxygen

Red arrows = respiration

Green arrows = photosynthesis

C3 photosynthesis ~ 95% of Earth’s plant biomass

Nearly all plant families (e.g., avocados, beans, rice)Ancestral pathway in plants

Autotrophs: Photosynthetic

Photo of “spirit bear” in C3-dominated Olympic Peninsula temperate rainforest from http://channel.nationalgeographic.com/wild/episodes/forests/

Autotrophs: Photosynthetic

Photorespiration

Rubisco catalyzes competing reactions

(1) Carboxylase rxn in photosynthesis

(2) Oxygenase rxn in photorespiration (unlike cellular respiration does

not produce ATP)

Image of model of rubisco from Wikimedia Commons

As pCO2 decreases relative to pO2, rate of photoresp. increases relative to PSN

As temp. increases,rate of photoresp. increases more rapidly than PSN

Autotrophs: Photosynthetic

C4 photosynthesis18 plant families, (e.g., corn, sugarcane)

Reduces photorespiration by biochemical & morphological (spatial segregation of CO2 uptake & Calvin cycle) specialization

Photo of wildebeests in C4-grass-dominated Serengeti tropical savanna from Wikimedia Commons

Outperform C3 plants at high temp., low [CO2], and most have greater water use efficiency

Autotrophs: Photosynthetic

CAM (crassulacean acid metabolism) photosynthesis33 plant families (e.g., pineapples, nearly all cacti)

Temporal separation of CO2 uptake & Calvin cycle in succulent organs

Image of various species of the family Cactaceae from Wikimedia Commons

Open stomates at night, so high water use efficiency

Especially prevalent in arid or saline environments; also in

some aquatic plants

Some plants employfacultative CAM

Isotopes

# Neutrons

#Protons

6

7

6 7 8 9

14N 15N

12C 13C 14C 15C

13N 16N

XXXX = radioisotope = stable isotope

isotopes

Nonradioactive; differ in number of neutrons; lighter form much more abundant in nature;

heavier form generally discriminated against in chemical rxns

Stable Isotopes

=𝑅𝑠𝑎𝑚𝑝𝑙𝑒−𝑅𝑠𝑡𝑎𝑛𝑑𝑎𝑟𝑑

𝑅 𝑠𝑡𝑎𝑛𝑑𝑎𝑟𝑑𝑥1000

𝑅=𝐻𝑒𝑎𝑣𝑦 𝑋

h𝐿𝑖𝑔 𝑡 𝑋

𝑅=13𝐶12𝐶

𝑅=15𝑁14𝑁

13C helps identify PSN pathway

Stable Isotopes

Cain, Bowman & Hacker (2014), Fig. Ecological Toolkit 5.1 A

Atmospheric 13C ~ -7

Obtain energy by oxidizing inorganic compounds, to fuel Calvin cycle, or other biochemical pathway, to fix carbon

Autotrophs: Chemosynthetic

Cain, Bowman & Hacker (2014), Table 5.1

Redox rxn: reductant transfers electrons to oxidant

Heterotrophs

Photo of a tailless whip scorpion consuming a newly eclosed cicada courtesy of Greg Dimijian

Herbivores, carnivores, omnivores, detritivores, as well as organisms that obtain sustenance through coprophagy, geophagy, etc.

obtain energy from organic compounds

Heterotrophs

Cain, Bowman & Hacker (2014), Figs. 5.18

Chemical constituents of food vary by energy content & ease of assimilation

Holoparasite

Photo of Rafflesia from http://natureafield.com/rafflesia-a-lovely-giant-parasitic-flower/

A heterotrophic plant – lacks chlorophyll & parasitizes other plants

Hemiparasite

Photo of mistletoe from Wikimedia Commons

A photosynthetic plant that partially parasitizes other plants (partial autotroph / partial heterotroph)

Agriculture in attine ants

Heterotrophic Fungus-Gardening

Photo of leaf-cutter ant shadows through a leaf from Christian Ziegler and of a fungus garden from Alex Wild

Stable Isotopes

Figure from Meehan et al. (2009)

An herbivorous jumping spider (Bagheera kiplingi) that exploits

an ant-plant mutualism (Vachellia [formerly Acacia] &

Pseudomyrmex)

15N helps identify trophic level

Myriad adaptations for finding & obtaining food, consuming food, and absorbing its energy & nutrients

Heterotrophs

Mouthparts of butterfly, ant & fly from Wikimedia Commons

Adaptive Phenotypic ConvergenceE.g., In 1835 Darwin thought the green warbler-finch (C. olivacea) was a wren!

Heterotrophs

John Gould’s drawings of Darwin’s finch specimens & photo of Bewick’s wren from Wikimedia Commons

Thraupidae Troglodytidae

Convergent

evolution

Adaptive Phenotypic Divergence:Sexual dimorphism in the Huia (an extinct New Zealand wattlebird)

Heterotrophs

Image of male (foreground) & female (background) from Wikimedia Commons

Adaptive Phenotypic Divergence & Radiation:Morphological diversity among Hawaiian honeycreepers

Heterotrophs

Image from http://www.hawaiiecoregionplan.info/FBC.html

Ecologically or sexually selected?

The human body contains about 10x the number of microbial cells as human somatic cells

Microbiome (genomes) / microbiota (microbes)

Photomicrograph of Escherichia coli of human gut flora from Wikimedia Commons

Geoff West, Brian Enquist & James Brown

Metabolic Theory of Ecology

Photo of West, Enquist & Brown from: http://www.salvias.net/~brian/Department_of_Ecology_and_Evolutionary_Biology/MST.html

Allometry – Coined by Julian Huxley (1932) for the study of size& its relationship to characteristics within individuals(due to ontogenetic changes) & among organisms

(due to size-related differences in shape, metabolism, etc.)

Kleiber’s law: size is related allometrically to total basal metabolic rate in

birds & mammals:B M3/4

The red line’s slope = 1

Metabolic Theory of Ecology, Scaling & Allometry

Image from http://biology.unm.edu/jhbrown/Research/Scaling.html

Figure from West et al. (1997)

Proposed that many allometric relationships in biology are

governed by the physical properties of branching distribution networks

(e.g., blood vessels, xylem & phloem)

Metabolic Theory of Ecology, Scaling & Allometry