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207 test

adaptive form and function

Traits can only evolve if – (1) the trait exhibits variation, and – (2) that variation is heritable, and – (3) if there is variation among individuals in their lifetime reproductive success
Adaptive Evolution Traits can evolve in response to natural selection
Neutral Evolution Traits can also evolve due to genetic drift
Neutral evolution Variation in (a) trait value and (b) lifetime reproductive success But NO correlation between them
Neutral evolution Variation in (a) trait value and (b) lifetime reproductive success
When is evolution adaptive? Correlation between trait and reproductive success!!
How to test an adaptive hypothesis? 1Assess correlation between trait and reproductive success– Survival – Amount of food obtained – Mating success for a given period (2) Experiment (3) Comparative study of correlation between trait variation among species, and variation in other variables
How can correlational studies test adaptive hypotheses? Assess correlation between the variation in the trait of interest and variation in some measure of fitness eg Number of lambs fathered vs Male Horn length
3 main ways of testing adaptive hypotheses 1 Correlational Studies 2 Experiments 3 Comparative Method
How can you test for a coevolutionary arms race? We can assess whether a trait in a prey species is an antipredator adaptation by looking at the covariance between: – Prey phenotype and predator fitness
How can you test for a coevolutionary arms race? Use the fossil record – Requires morphological trait that may influence predator/prey interaction • Use a comparative approach comparing multiple living species
Cooperative hunting Living in a group can provide safety for prey species – Dilution (more chance someone else will get eaten) – More eyes to watch for danger – Many prey might be able to fight off a predator A number of predatory species also hunt in groups
African Wild Dogs Lycaon pictus Larger packs are more successful and kill larger prey
Spider web diversity First spiders probably had trapdoor webs • Then came horizontal cribellate (dry) webs • From here orb webs evolved • Web design then diversified greatly and in some groups was lost
Silk glands, silk types and web construction Major ampullate glands • Minor ampullate glands • Flagelliform glands • Aciniform glands • Tubuliform glands
Major ampullate glands – Draglines – Safety lines – Web frame – Web radial
Major ampullate glands Draglines – Safety lines – Web frame – Web radial Temporary capture spiral
Flagelliform glands Final spiral •Supporting core silkx •Coated with sticky droplets from aggregate glands
Aciniform glands Wrapping prey
Tubuliform glands Making egg sac
Is variation in web design adaptive? When supplemental prey were provided on night 5, web area and thread length dropped
Do spiders alter web architecture in response to prey type? Nephila pilipes build webs with wider mesh spacing when fed larger prey build webs with thicker silk when fed larger prey
Are prey attracted to decorations? y maze court more prey but also attracted more predators
Methods of avoiding predation Evasion Defence Signalling
Cryptic colouration is often polymorphic This is thought to inhibit learning in predators by preventing a ‘search image’ being formed • Polymorphism can occur within species e.g. Cepaea snails • Or between species e.g. Catocala moths
Difficult to determine if a predator has: not detected a prey item that resembles an inanimate object (e.g. a twig) – detected the prey item but has misclassified it as something else (chick example)
Masquerade! detected but looks like somethin else. for example stick instect maybe seen but is classified as a stick. detected but is classified as stick.
Toxins Biologically produced molecules that are harmful examples. Neurotoxins • Haemotoxins • Cytotoxins • Necrotoxins
Poisons Not necessarily produced biologically, or for the function of defence – Usually refers to substances that are ingested
Venoms Toxins that are delivered via a bite or sting
How can you study chemical defence? Anatomy and physiology of toxin production • Pharmacology of toxic effects • Evolution of toxins and glands • Costs/benefits of chemical defences
How does an animal become toxic? Synthesise toxins in specialised glands – Symbiosis with toxic microbes – Acquire toxins from plants or prey
Biosynthesis of toxins Many animals are able to synthesise toxic compounds from metabolic products • This usually occurs in specific glands where epithelial cells undertake biosynthesis • Glands or reaction chambers may provide protection to the animal producing the toxin
Sequestration of plant toxins Sequestration of plant toxins
Monarch butterfly lays eggs on milkweed Toxin is Calotropin
Tiger moth, Utetheisa ornatrix Larvae gain defensive pyrrolizidine alkaloids from plants and retain them through metamorphosis into adulthood • Wolf spiders reject larvae • Web building spiders cut adults from webs • Birds reject adults
Tiger moth, Utetheisa ornatrix The alkaloids are transferred to the eggs which, when laid on the host plant, are protected chemically against ants (which try to defend the plant)
Tiger moth, Utetheisa ornatrix Alkaloids are transferred from the male to the female when they mate, protecting the female male-provided alkaloids are used to protect the eggs Males advertise how much toxin by converting some toxin into sex pheromones for signaling to female
Tiger moth, Utetheisa ornatrix Females copulate with males with more of this pheromone • because the male transfers the rest of his stored toxin to the female during mating • and the female incorporates the toxin into her eggs to deter predators
Snake venom: Cholinesterase leads to loss of muscle control
Snake venom: Proteases digest tissues
Snake venom: Phosphodiesterases drop blood pressure
Snake venom: ATP-ase interferes with energy metabolism
Snake venom: Neurotoxins interfere with sodium channels
Snake venom: Haemotoxins destroy red blood cells
Reptilian venom evolution Salivary glands were modified into venom glands before the evolution of snakes
Where do frogs get their Batrachotoxins? There is now evidence for batrachotoxins being derived from the diet • Present in ants, mites, beetles, millipedes • Evolutionary switches in diet correspond with evolution of toxicity
Convergence in toxic defence In Madagascar, frogs of the genus Mantella also possess batrachotoxins, derived from ants and millipedes • Frogs are unrelated so represents a great example of convergent evolution
Does warning colouration honestly signal toxicity? The colour contrast of different frog species correlates with the potency of their toxins • Computers and humans agree that the more toxic frogs are the most contrasting
Mimicry One prey species (the mimic) has come to resemble the second (the model) which is regarded as “unprofitable” by predators. • The mimic may itself either be profitable (Batesian) or unprofitable (Müllerian)
Aggressive Mimicry A number of species mimic other animals (or plants) to fool their prey (rather than predators) • Some ant mimics are myrmecophagous (feed on ants) so they fool the ants as well as potential predators
Homeostasis Regulation of internal environment within narrow limits  Important for all physiological functions  Essential for life in hostile / varying environments
Homeostatic feedback Continuous sampling and regulation •E.g. Thermoregulation & negative feedback Sensors (warming) >Brain (Hypothalamus acts as “thermostat”> Shivering / vasoconstriction = then loop
Negative feedback control Thermoregulation (mammalian)Feedback analogous to lab thermal bath Temp sensor (compares temperature against setpoint) Heater Thermostat If cold: heat produced If hot: heating switched off
Homeostatic feedback E.g. Ovulation and positive feedback Hypothalamus (brain) > GnRH > (Adenohypophysis (brain) >LH +FSH >Ovary: follicle development = Estrogen is the loop feedback.
Homeostasis and cellular composition The problem faced by cells Unavoidable movements of: •Salts and solutes (diffusion) movement from strong (hyper) solution to weak (hypo) solution. Water goes from hyper to hypo bring both solution to equilibrium
Homeostasis:  Freshwater fish Blood more concentrated than environment mean Gain water (swelling) copes by exrecting dilute urine and not drinking. copes with lose of salt by reating salt via kidney tubule. gaining salt from food & active transportation through gills
Homeostasis: Saltwater fish Blood less concentrated than environment cope losing water Lose water by SW copes with gain of salt by exreting salt via active transporatoin across gilles
Rate of energy consumption = metabolic rate (Cal or J) = rate of heat production = rate of O2 consumption)
ATP production ADP + Pi + energy from food molecules =>ATP
ATP consumption: ATP => ADP + Pi + energy usable by cell processes
Aerobic Metabolism 4 major sets of reactions: •Glycolysis • Krebs Cycle • Electron-transport chain • Oxidative phosphorylation these Pathways that (by use of O2 ) oxidise foodstuff molecules to CO2 and H2O and capture ATP • All major food classes oxidised
Aerobic Metabolism Glycolysis: • Enzymatically catalysed reactions • Glucose oxidised to 2 molecules of pyruvic acid • Cytosolic 2 x ATP molecules (net) per glucose 2 x NADH2 molecules
The Krebs cycle (citric acid cycle) • Pyruvic acid oxidised in cyclical enzymatic reaction 6 x CO2 molecules 8 x NADH2 and 2 x FADH2 2 x ATP molecules per glucose (GTP donates Pi to ADP)
The Electron Transport Chain NAD and FAD regenerated (oxidised) via 4 protein “chain” complexes • Sequential shift of electrons Complex IV passes electrons to oxygen (reduced to water) •O2 = final electron acceptor
Oxidative phosphorylation Each complex produces 1 ATP per pair of electrons = 3 ATP from NADH2 = 2 ATP from FADH2
Oxidative phosphorylation NADH2 Glycolysis: 2 x NADH2 Krebs: 8 x NADH2 = 10 NADH2 x 3 = 30 ATP
Oxidative phosphorylation FADH2 Krebs: 2 x FADH2 = 2 x 2 = 4 ATP = 34 ATP total Other phosphorylations = 4 ATP net ATP = 38 total for all cycles
The problem of O2 deficiency for aerobic metabolism Electrons entering electron-transport chain not discharged • Oxidative phosphorylation stops = 34 (of 38) ATP molecules not produced • Cells’ supply of NAD and FAD threatened (redox imbalance)
Anaerobic glycolysis Pyruvic acid reduced to lactic acid •Redox balance maintained -NADH2 re-oxidised to NAD = > ATP produced without O2
Phosphagens • Temporary stores of high energy phosphate bonds • Vertebrate and Invertebrates • Phosphagen kinases
TUNA Not much O2 in water BUT tunas don’t stop swimming! • Rapid O2 uptake with efficient respiratory system •Gills (8x surface area) •Thin gill membranes (0.6 vs. 5m) •Ram ventilators (no buccal-opercular pumping) • v high rates of water flow
Ventilation: Active ● Energetically expensive BUT ● Reliable, controllable and vigorous ● Very common A) Unidirectional (e.g. Fish gills) B) Bidirectional (tidal) (e.g. Mammalian lungs) C) Nondirectional (e.g. external gills)
Amphibians:Examples of various designs Bucco-pharyngeal pumping (relic of piscine ancestry) ● Fills buccal cavity before emptying lungs offsets mixing (stale air)
Mammals:Examples of various designs Gas in the respiratory airways is different! - Speed: Motionless (gaseous diffusion) - Composition: Mixes with stale air (12% fresh; 88% stale)
Non-bird Reptiles:Examples of various designs Unicameral Lungs = Simple sacs (anterior perfusion) Multicameral Lungs = Multi-chambered - Active / aerobic species
Bird lungs: Examples of various designs Lungs yet cross-current exchange??? ● Lungs are structurally different LSA / thin membranes ●Unidirectional flow (parabronchi) ●High altitude flying
Blood : Organic constituents Hormones •Vitamins •Plasma proteins •Globulins (immunity) • Buffering and osmotic proteins (albumin, transferrin) •Antifreeze glycopeptides (glycoproteins) ~50% of osmolality
Blood : Celllular constituents Erythrocytes - Red blood cells (O2, CO2 and H+ exchange) • Leucocytes - White blood cells (immunoprotection)
Haemoglobin Tetrameric globular protein • 2 alpha and 2 beta polypeptides •O2 binding heme (protoporphyrin) •Increases the carrying capacity of O2 , CO2 , H+ = Reduced demand on circulation
What is stress Physiological context: “The response to any demand causing an extension of physiological state beyond normal resting values” General context: “ Stress is a threat to or disturbance of homeostasis”
Stressors Environmental (O2 , CO2 , pollution) • Handling / angling (exhaustion) • Social (competition) • Psychological
Is stress adaptive? Acute stress Evolved as adaptive response Non-essential resources diverted Cost to growth, reproduction etc Chronic stress responses Unable to escape Adaptive value compromised in the long term Detrimental side effects
Stress: General adaptation Syndrome Hans Seyle (1950): 1. Primary stress response “Alarm reaction” “Fight or flight” • Hormonal cascade • Behavioural
Stress: General adaptation Syndrome Hans Seyle (1950): 2. Secondary stress response “Adjusting phase to regain homeostasis” • Caloric energy cost • Metabolic, cardiovascular, Acid-base status, haematological, behavioural
Stress: General adaptation Syndrome Hans Seyle (1950):3. Tertiary stress responses “Stage of exhaustion” (chronic response) • Growth, FCR, behaviour (e.g. spawning), disease, reproduction, mortality, community
Role of catecholamines Cardiovascular >up • HR & stroke volume > up • Vasoconstriction >up • Gill perfusion > up Metabolism > up • Blood glucose > up • FFAs > up • Osmoregulation > down Haematological > up • Hb-O2 affinity > up
Role of cortisol = Energy mobilisation Metabolism > up •Blood glucose > up = fuel • Proteolysis > up • Lipolysis > up • Gluconeogenesis > up •Maintains high lactate Osmoregulation > up •SW tolerance Reproduction > down • Vitellogenin synthesis > down •Inflammation / immunity > dwn
Hypoxia What is it?
Air-breathing (AB) evolution First evolved during the Late Silurian (438-408 mybp)
Sherman, P. M. (1994). Animal Behaviour, 48(1), 19-34. No significant change in web dimensions. When supplemental prey were provided on night 5, web area and thread length dropped species = Larinioides cornutus
Tso, I. M., Chiang, S. Y., & Blackledge, T. A. (2007). Ethology, 113(4), 324-333. Nephila pilipes build webs with wider mesh spacing when fed larger prey Nephila pilipes build webs with thicker silk when fed larger prey
Bruce, et al.(2005) Journal of Evolutionary Biology, 14(5), 786-794. Y-maze prey 15 v 6 on decorated web. predator 9 v 1
Created by: JIB