PSYU3352 Lectures 1 & 2 PDF

6/1/22 Introduction Appetite: The psychology of eating and drinking 1 1 Introduction Who am I? (contact: dick.stevenson@mq...

6/1/22 Introduction Appetite: The psychology of eating and drinking 1 1 Introduction Who am I? (contact: [email protected]) Why am I teaching this course? Tutorials – Tutorials start next week – Please try to remain in the same tutorial class Please obtain: – The course handbook from iLearn (info about everything) Please ensure that you read the Course Handbook – You need to do so to understand how your project will work and how this is linked to the tutorials – It also contains the course timetable and other vital information which will help you to do well 2 2 1  6/1/22 Why study feeding & drinking? Eating and drinking are essential to survival Consequently, much of our behaviour, physiology and anatomy has been shaped by evolutionary forces related to ingestion Colour vision (from primates and ripe fruit) Liking for junk food (hard wired for sugar and fat) Disposition to gain weight not lose it (saving fat to survive famines) Bipedalism for predator detection and hunting (running) Gut and teeth design, and face structure (chewing) Understanding feeding behaviour (and its physiology) is important for several reasons 3 3 Why study feeding and drinking? In the developing world around 1.2 Billion (1200 million or about 60x the population of Australia) people are malnourished, underweight and hungry, yet in the West, 1.2 Billion people are overweight or obese This is important because malnourishment kills, lowers IQ, cuts earnings and entrenches poverty; Obesity shortens lifespan, induces chronic diseases and is very costly What biological, psychological, social and economic factors contribute to obesity and malnourishment? Why are some people starving whilst others are eating themselves into an early grave? 4 4 2  6/1/22 Why study feeding and drinking? In the west 15% of individuals are alcohol dependent, with 100,000 preventable alcohol related deaths/year in the US alone What biological, psychological, social and economic factors contribute to alcohol dependence? And we might now add processed food as well when we think about dependency – Mice preferring sugar to cocaine – Mice withdrawing from sugar 5 5 Why study feeding and drinking? Eating disorders - especially anorexia which is the most lethal of all psychiatric conditions - affect approximately 1-2% of college-age women in the West Eating disorders seem to be coming more common, and they are also involved in obesity, notably binge eating disorder What biological, psychological, social and economic factors contribute to eating disorders? 6 6 3  6/1/22 Answers? To study these varied conditions - obesity, alcoholism, starvation, malnutrition and eating disorders - we need to know how eating and drinking (ingestion) occur normally – Why do we choose to eat certain things and not others? Lamb chops over human chops, chips over apples…. – How do we perceive food and drink? Why is fat, fatty and chilli pepper, hot? – What starts and stops eating? How do we get hungry and full, and are we in charge of what we eat or are we physiological zombies? – What societal factors influence ingestion? Why don’t we eat‘desert shrimps’(and other insects)? – What economic factors govern eating and drinking? Fast food, dual incomes, cars, TV and obesity… – In fact as you’ll come to see, the whole structure of our society seems engineered to help us eat more and move less 7 7 Course structure Consequently… – We will start (today) by examining the basics of ingestion: Energy metabolism Food types The digestive system Water balance Eating and drinking strategies used by us and other animals 8 8 4  6/1/22 Then… Over the coming weeks we will look at: How we perceive food and drink The nature of thirst, and food-related drugs Food preferences Food taboos (why we don’t eat people and pets) The psychobiology of food intake The food system (farm gate to the plate) Finally, we will turn to obesity, starvation, eating disorders, body image, dieting and related topics 9 9 Things you need to know Format – Lectures and videos/films The lectures are all presented online via Echo360 I will try and arrange a session to watch the videos/films, as these cannot be shown via iLearn/Echo due to copyright constraints Please note that the videos/films DO NOT form part of the exam We will have one special class in the final teaching week for questions, revision etc (zoom link will be available on iLearn) – Tutorials All the tutes are online via zoom, with the class links on iLearn The tutorials are there to support your personal research project through its design and implementation to its analysis and write-up Please read the course handbook for details 10 10 5  6/1/22 Things you need to know Reading – Each week there are several compulsory pieces of reading (lecture notes, Logue chapter[s] & tutorial paper/s) – Logue is the course textbook (‘The psychology of eating and drinking’4th Edition) – There are also other supplementary references listed in the course handbook (for your interest and edification) 11 11 Things you need to know Assessment (details in Course Handbook) – End of semester exam (Multiple choice) - 50% Based upon – Lectures (but NOT the films/videos or the special class during the final week ) – Material from Logue – The exam will (as things stand) be conducted in person at Macquarie University (North Ryde campus) 12 12 6  6/1/22 The lms and videos won't be part of the examinable material but the lectures and your Logue et al. textbook will be examinable. Things you need to know Assessment (details in Course Handbook) Your personal research project (Report) – 50% – This will be a project where you serve as experimenter and participant (i.e., covid-proof) – The basics of how this will work are detailed in the course handbook – Please make sure you read the relevant material in the course handbook, and the associated tutorial papers, before your first tutorial – The first tutorial is in Week 2 Please check the course handbook to see the project timeline, when the tutorials are etc, so you are prepared 13 13 Energy metabolism The basic purpose of food is to provide energy Food provides chemical energy which the body converts into – Mechanical energy (muscles) – Electrical energy (nerves) – Heat (maintaining optimal temperature) – Other forms of chemical energy (fat; proteins) The key food constituents that provide energy are carbohydrates, proteins and fats 14 14 7  It's important to note that the body's metabolic pathway can convert energy from fats, proteins and carbohydrates 6/1/22 (macronutrients). If you're dieting a lot of diets focus on simply removing fats. However, you also have the option of limiting proteins and carbohydrates as well whilst dieting. There isn't only one way to loose weight. We haven't been able to nd a reason as to why Main metabolic pathways the brain is The liver has 100g of glycogen Liver 100g completely reliant Muscles 500g on glucose. One c. Lactic acid cycle - muscles theory is that a. Brain/CNS because if the 20-40% of body mass brain relied on other things such as proteins it could b. All other tissue damage the brain. 1. Three principal methods of generating energy – metabolic pathways (in red) a (Glycolysis), b (Kreb’s cycle, aerobic), c (Lactic acid cycle, anaerobic) Fitness determined by capacity to get oxygen to muscle (VO2 max) 2. Two principal methods of energy storage (in green) 3. Note that all energy sources can be converted to fat 15 15 It doesn't matter if your diet was completely composed of protein or carbs or fat. Any of those macronutrients can be stored by your body as fat. So you can get fat on protein, carbs or on fat. Your body is very e cient at converting these to fat. Measuring the ‘energy’ in food The measure we will use is the Kcal (kilo calorie) – To convert to the SI unit, Kilo Joule (KJ), multiply the Kcal value by 4.184 One Kcal is the energy needed to raise 1L of water by 1 degree centigrade This is measured using a bomb calorimeter The amount of energy contained per gram, differs for fats, carbohydrates and proteins – Proteins & Carbohydrate yield 4 Kcal/g – Fats yield 9 Kcal/g – (Alcohol yields 7 Kcal/g) This is why fats are called energy dense foods 16 16 8  6/1/22 Pregnancy or other demands on the body will raise What are the bodies energy needs? their BMR. Illness e.g. a fever and At rest, the body expends considerable energy - termed the basal metabolic rate (BMR) your body is in attack mode Most of the food (i.e., energy) you consume goes to maintaining your BMR – about 70-80% against the pathogen BMR includes energy for cellular physiology (pumps), breathing and blood flow, muscle tone and protein sometimes this synthesis (e.g., immune system) can triple your Women need about 0.9 Kcal per kg/hour of bodyweight to BMR. maintain BMR and men around 1.0 Kcal per Kg/hour Over 24 hours, a 70 kg man would need around 1680 Kcal Babies have a just to maintain BMR (i.e., 24x70x1.0) high BMR because they BMR varies a lot dependent upon lactation, pregnancy, muscle/fat bulk, physical fitness, illness and age need to generate 17 heat and it lowers as they age. 17 Fat is less metabolically active than muscle, muscle burns more energy. Which is why men need slightly more Kcal to maintain their Basal Metabolic Rate (BMR). Activity On top of BMR we expend additional energy on ‘doing things’ To give you some idea here is the amount of energy you would expend if you did these ‘things’ for one hour (for a 70 kg person) – Shopping 190 Kcal – Walking 300 Kcal – Running 750 Kcal (see https://healthhub.medibankhealth.com.au/calculators/energy-expenditure/) To put this in perspective… – A big mac provides 550 Kcal, a standard sized mars bar 224 Kcal, and an apple 52 Kcal – So… 3hrs of hard shopping burns away a big mac, while 5 mins of running burns away an apple 18 18 9  6/1/22 Calculating energy needs Most tables that report the caloric intake that you need are based upon calculating your BMR and then estimating a light to moderate level of activity – Very light (BMR x 1.3) – Light (men x 1.6, women x 1.5) – Moderate (men x 1.7, women x 1.6) – Heavy (men x 2.1, women x 1.9) Most westerners have activity levels that are typically in the very light to light range 19 19 Heavy would be being physically active for 7-8 hours a day) E.g. a Lumberjack Consequences According to standard tables then, an 85 kg man (Mr Average in Australia [Ms weighs in at 71kg]) would need around 3270 Kcal / day (with light levels of activity) To put this in perspective, Mr Average in Australia eats around 3400 Kcal / day At the other end of the spectrum Nazi concentration camp inmates were fed about 700 Kcal / day It is not surprising then that many Australian adults slowly gain weight and that many camp inmates died of starvation 20 20 10  There are two types of Carbohydrates divided into two groups. Monosaccharides and Discaccharides. (Simple carbohydrates) Monosaccharides Glucose 6/1/22 Fructose; it's not found in many high concentration naturally. Mostly ripe pears. Galactose Discaccharides Are two Monosaccharides joined together. Sucrose; is a People in the US combination of consume a glucose joined to a Carbohydrates approximately 30 tsp of sugar per day. fructose. Types 1lb = 0.45kg Lactose is a - Simple combination of - Monosaccharides glucose and galactose - Glucose – corn, grapes E (which is not - Fructose – honey, many fruits particularly - Galactose – avocados sweet) - Discaccharides Maltose is - Sucrose – ‘sugar’ composed of - Lactose - milk sugar two glucose "molecules" - Maltose - beer together. - Complex - Polysaccharides (starch, High fructose corn syrup (HFCS), used in cellulose) Inulin aswell soft drinks mainly in the USA. Quantities Function consumed have increased enormously. In 1955 an average soft-drink serve was – Primarily to provide energy 207ml, it is now around 600ml. 21 21 Cellulose forms bre and inulin [a complex of sugar present in the roots of various plants and used medically to test kidney function. It is a polysaccharide based on fructose] is something that we can't break down either which contributes to bre in our diet. LDL Low HDL High Density Density Lipoproteins Fats Lipoproteins Or more properly Triglycerides A glycerol with three fatty acid tails Types (These are the different types of tail the glycerol can have) - Saturated (animal, coconut, palm) – some may increase LDL (bad cholesterol) - Monounsaturated (olive oil, canola) – some may increase HDL (good cholesterol) - Polyunsaturated - Omega 6 (vegetable) - Omega 3 (deep sea fish) – may increase HDL and lower LDL - Trans-saturated They are very resistant to going rancid (they don't oxidise) - Artificially produced from Mono or Polyunsaturated fats - Have significant commercial benefit/use (storage/non-animal) - Have negative health consequences (CHD, Diabetes, Obesity) - Health controversies – fats and heart disease Function of fats – Structural (nerves), Hormone synthesis, Fat soluble vitamins, Insulation & Padding, Energy storage (fats help the myelin sheath) 22 22 You don't need to eat fat to get fat. Also, the Scienti c community is really split on whether saturated fats cause heart disease. 11  6/1/22 Essential implies that we can only get them from our diet Protein Types – All proteins built from Amino acids – Some are essential and some can be synthesised by the body (meat provides all essentials, but combinations of vegetables and legumes can do so as well) Function – Tissue maintenance & growth, Hormone, Enzyme and Protein synthesis, Fluid balance, Energy The body also needs certain Minerals and Vitamins and these are termed micronutrients… 23 23 Micronutrients - Vitamins Deficiencies relatively rare in Western nations, yet almost a third of the US population consume them (supplement sales are a 30 Billion US dollar industry) Fat soluble vitamins (A, D, E & K) – A (eyes, skin, bones, reproduction & immunity) - Night blindness, xerophthalmia – D (bone formation, hormonal control) - Rickets – E (cell membrane integrity) - Hemolytic anemia – K (blood clotting) - Infant haemorrhage (hence neonatal K shots) Vulnerabilities after obesity surgery & lipase inhibitors Water soluble vitamins (C, B1, 2, Niacin, 6, Folate,12, Pantothenic acid, Biotin) – C (collagen formation, iron absorption) - Scurvy – B1 (energy metabolism) - Beri beri (thiamine & Korsakoff’s syndrome) – B2 (energy metabolism) - Glossitis, Seborrheic dermatitis – Niacin (energy metabolism) - Pellagra – B6 (amino acid synthesis) - Anemia – Folate (DNA synthesis) - Anemia, (Neural tube defects in pregnancy) – B12 (DNA synthesis) - Renal failure – Pantothenic acid (energy metabolism) - Burning feet syndrome – Biotin (protein metabolism) - Hair loss 24 24 If you have obesity surgery one of the consequences of that is that your body becomes much less e cient at absorbing fat. Which is why in the early days, patients would develop micro nutritional de ciencies such as rickets etc. 12  6/1/22 Micronutrients - Minerals Most Westerner’s have too much sodium (as Salt [consume 10+g/day, RDA 3-6g/day]) and too little calcium Macrominerals (100mg/day+) – Calcium (osteoporosis affects 25M in USA - bones, clotting, cellular function) – Phosphorus (1% of Body Weight - metabolism) – Sodium (water balance, nerves) – Potassium (water balance, nerves) – Magnesium, Chloride & Sulphur Microminerals (100mg/day-) – Iron (5g in total - hemoglobin) – Iodine (thyroid function) – Fluoride, Selenium & Zinc (and several others…) 25 25 If you're iron de cient you may nd yourself eating ice which is a condition called Pagophagia.🧊 🧊 A desire to chew and crunch on ice. Human digestive system The basic function of the digestive system is to efficiently extract nutrients from food We can characterise the digestive system as having two major parts – Main organs (stomach, intestines) – Accessory organs (liver, pancreas, gallbladder) Food is broken down mechanically, chemically (acid) and by enzymes How does it work? 26 26 13  6/1/22 Human digestive system – gross anatomy Mouth – saliva, amylase and mechanical action Stomach Small intestine Duodenum, jejunum, ileum Accessory organs Large intestine Colon, rectum Water re/absorption & compaction The colon contains our gut microbiome. 27 27 Stomach Food is received in the upper part of the stomach (fundus) where it is mechanically ground into particles 1-2mm in diameter It is then mixed with stomach acid and enzymes to form a semi-liquid fluid called chyme, collecting in the lower part of the stomach (antrum) After the stomach discharges its content into the gut, it starts to make rhythmic contractions that you may associate with hunger 28 28 14  6/1/22 We don't know if there's a relationship between how small or large someone's small intestine is and their propensity to gain weight. Small intestine (SI) It is about 2.5-3 cm in diameter and 6-7 M long (ranges from 4-10 M) and 90% of chemical absorption from food into the body happens here Food in the SI triggers CCK release and the accessory organs release bile (500ml/day) and pancreatic juices Bile breaks down fat Pancreatic juice breaks down protein and carbohydrates (gut secretions assist too) The products of digestion move through the SI wall (up to 60M2 surface area) into the HPV (hepatic portal vein) and travel to the liver and thence to the body’s cells 29 29 Large intestine It is about 1-2m long It consists of four parts – Cecum – Receives digested matter from small intestine (appendix) – Colon – Removes remaining water and bacterial action results in the formation of B & K vitamins which are absorbed – Rectum – Temporary storage – Anal canal – As one would imagine 30 30 If you take a gram of material form the colon (it has the highest microbial density of any habitat on earth). They are extraordinarily rich viral and microorganism habitats. They a ect our chances of becoming obese and that in turn a ects our gut biome, brain and mental health. 15  6/1/22 Water balance Apart from oxygen, water is our next most important need (followed by food) You can last upwards of 28 days+ without food, but only a few days with no water (less with physical exertion and a hot climate) Function – Medium in which all chemical reactions occur Cellular & Interstitial water - 28L (for 70Kg person) Blood - 5L (for 70Kg person) Gut - 10L (for 70Kg person) – Its presence is crucial for energy release – Temperature regulation etc 31 31 Interstitial just means the spaces around cells. Water balance The body looses around 2.2 litres per day – Lungs 400ml – Sweat 600ml – Faeces 200ml – Urine 1000ml (via Kidneys filtering blood) To maintain water balance we therefore need to drink about 1 litre (thirst), with the remainder coming equally from food and the byproducts of energy release (metabolic water) 32 32 16  6/1/22 Conclusion I have covered this material with one goal in mind, so that you have all the basic concepts when we start to look in more detail at various aspects of ingestion, drinking, obesity etc We will now turn to a further introductory issue - how animals (and humans) go about the business of obtaining food and drink 33 33 Feeding strategies in animals Appetite: The psychology of eating and drinking The larger its claws are, the less poisonous it is. (The Scorpion) 34 34 17  6/1/22 Introduction The animal kingdom has managed to exploit just about every possible source of food Take the clam for example, whose muscle (meat) is well protected within its thick shell – Certain mollusks drill through its shell to get the meat – Starfish clamp to the shell and slowly prize it open – Herring gulls drop the clam on to rocks to shatter it – Otters find a rock then break the shell As you can see from this example, no food source, even one as impregnable as the clam, is safe! 35 35 Adaptive radiation The purpose of this lecture is to illustrate this diversity - that is the adaptive radiation of feeding strategies driven by the need to secure food We will do this by examining the principle types of feeding strategy that animals adopt This allows us to see where in this big picture human eating behaviour fits in and the sort of questions that we might ask about feeding behaviour in general 36 36 18  6/1/22 The need for food Obtaining energy to live and hence reproduce is a primary goal for all animals and they spend much of their time focused on feeding From the perspective of our century and our society, it is very difficult to believe the importance of food for survival Yet today, during the hour of this lecture, 350 children will die directly as a result of lack of food Industrialised countries have built an effective food system, but it is more fragile than we might care to imagine and you don’t have to go back that far in time to get to our hungry past... 37 37 What constrains feeding strategies? The animals size (Predatory mite vs Tiger) Genes (behavioural/physiological flexibility) Where it lives – In the sea & fresh water, majority of plant biomass is as algae – On land, greater variety of plant forms – In the air, primarily other animals – Water & Air offer 3-D environments, Land just 2-D 38 38 19  6/1/22 Classifying feeding strategies in animals Herbivores (e.g., Rabbit) – Eat vegetation, primary energy producers Carnivores (e.g., Lion) – Eat herbivores & carnivores, living & dead Parasites (e.g., Tape worm) – Obtain energy from a host Omnivores (e.g., Rat, roaches and us) – Eat vegetation & animals We will now look at each of these in turn 39 39 Feeding in herbivores General characteristics – Spend considerable time eating – Process large volumes of food – Food has low protein content – Retained for long periods in the gut – Long guts to maximise digestion – Have to deal with cellulose – Have to avoid being eaten Specific approaches 40 40 20  6/1/22 Grazing Grazing is one approach to feeding used by herbivores Grasses offer one source of food that is suitable for grazing Grasses are an ‘ideal’ food source – Easily accessible & widespread – Palatable – Tolerant (50% annual produce can be eaten) Most grass grazing animals are mammals Special adaptations to grazing grass include: – Teeth (cutters and grinders) – Continuous eating & coprophagy – Symbiotic cellulose digesting organisms (enzymes) – Escape strategies (numbers, camouflage, speed) 41 41 Herbivore guts for grazing 42 42 Note how long the sheep's intestines are, but also how much more complex it is in comparison to our own digestive system. 21  6/1/22 Flowers, fruits and seeds Animals specialising on these food types include pollen feeding insects, birds, bats and monkeys Many species of monkey specialise in eating fruit – Not only did this lead to the ‘re-evolving’ of colour vision it also requires considerable behavioural flexibility to exploit this food source Chimps may bite fruit that is not yet ripe to promote ripening Considerable mnemonic skills are needed to remember seasonal location of fruit and its nutritional value This information amounts to a form of ‘food culture’ which is then passed on to subsequent generations We're talking about 100,000's location and food culture which is passed on from generations so that chimps can exploit this food source. 43 43 Hummingbirds The hummingbirds are another example of this group – Some weigh 2g and so have large surface area to mass with enormous heat loss and thus need for energy – They have a heart rate of 1000/min and breath at the rate of 250/min – Many eat their own bodyweight in nectar each day and are only hours away from starvation – At night they enter a state termed ‘torpor’, where they slow their metabolism so as not to starve 44 44 22  6/1/22 Other herbivores Plant chewers and suckers – e.g., Elephants, koalas, sloths & aphids Plant burrowers – Primarily insects Deposit and suspension feeders – Marine organisms feeding on dead plant material Faeces/Rotting vegetation – 2000 species of dung beetle alone in Africa and these deserve special mention… 45 45 Dung beetles Dung beetles feed on the liquid component of faeces - herbivores being the favourite Three major types – rollers, tunnellers and burrowers – Commonest are the Rollers - balls of faeces are rolled and buried underground both as a food supply and to feed their larvae – The beetles are very strong, and can roll dung well in excess of their body weight (10x +) The beetles will also attempt to steal balls and fight over them Without these beetles fly levels would be astronomical – Dung beetles save an estimated 300 million US$/year in faeces disposal for the US livestock industry 46 46 23  6/1/22 Herbivores - conclusion A considerable focus for us in this course will be intake control and food choice Concepts such as hunger and satiety may have little meaning for animals whose ‘meals’ are continuous In addition, many feed on few plant species, yet do not apparently tire of this repetitive diet In many respects the issues of most interest to us about human diet appear irrelevant for herbivores 47 47 Feeding in carnivores General characteristics – Most spend relatively little time eating but more time attempting to obtain prey – with some very notable exceptions (filter feeders) – Preference for different prey therefore depend upon weighing the cost of the food against its benefit (note parallel to human preference for fatty and sweet foods) – Their food is higher in protein and lower in volume than herbivores (H’s), so shorter guts – Carnivores will often eat to capacity when food is available (a Wild cat can eat 1/3rd of its own body weight in 1 sitting) – Whilst H’s show adaptations to avoid being eaten, C’s show adaptations which favour catching food H's = herbivores C's = carnivores 48 48 Cost bene t trade o concerning hunting them and the amount of reward you get for catching them and we see this same parallel in humans. Most humans prefer sweet and fatty foods because they give us more bang for our buck (more high energy) and our brain is hard-wired to seek out and enjoy these foods. 24  6/1/22 Carnivore guts 49 49 Types of predator Browsing predators – Typically mollusc/sea slugs grazing colonial marine animals – Certain filter feeders E.g. Whales Hunters – Actively seek prey Stalkers (lions, leopard seals) Stealth feeders (mosquitoes, vampire bats) Carrion eaters – Dead animals or scraps Some examples… 50 50 25  6/1/22 Filter feeders These are water living organisms such as baleen whales, certain sharks and fish The baleen whales are the most interesting example of this group The blue whale (right) is the most spectacular of them all 51 51 The blue whale – An adult blue whale is the largest creature that has ever lived – It can weigh 150,000kg and be 30m in length, the same sort of size as a Boeing 737 – Yet these whales eat shrimps/krill, the largest of which is 7.5cm in length – This is accomplished by having 300 baleen plates which hang down from the mouth – Water (rich in krill) is taken into the mouth and forced out through the baleen plates leaving the krill behind – The whales stomach, when full, can hold up to 10,000kg of food 52 52 26  6/1/22 Stalking - Leopard seals Leopard seals are natives of Antarctica and hunt mainly penguins and seals Adults are about 3m and weigh around 370kg They cruise beyond the ice awaiting penguins diving in They then swim rapidly and grab the penguin’s feet beating it on the water till it is flayed alive They will also attack and kill humans 53 53 They mostly prey on cattle e.g the sleeping cow and bites into the mammal and their saliva has a potent anesthetic that also prevents clotting. Stealth - Vampire bat They hunt at night and approach their sleeping mammalian prey on the ground They detect blood vessels with heat sensors They bite and ingest blood whilst their saliva prevents clotting The bat may not be able to fly after food and has a specially adapted urinary system to off- load excess fluid The bats share food (regurgitated blood) to other (non-related or related) members of their colony who have not been able to feed 54 54 27  6/1/22 Carrion - The vulture Vultures can detect prey at many miles both by sight and smell They feed to the point where they become so full they have to rest before flying again Note the featherless head on this Kettle vulture (right) adapted for sticking into blood and guts The use of diclofenac in farm animals has led to a mass loss of vultures in Asia, leaving animal carcasses rotting where they lie It has also threatened the viability of human‘sky burial’in Tibet 55 55 Carnivores - conclusions Carnivores (with some notable exceptions) eat few meals, but when they do, they eat to repletion, diet being somewhat limited repletion; eating to excess Hunger and satiety do appear relevant concepts here, unlike with herbivores Yet the ‘meal’ concept is very different from us as large time intervals (days) may separate feeds Still carnivores share more common features with our eating behaviour than herbivores do 56 56 28  6/1/22 Feeding in parasites Definitions: When is a parasite a parasite? – The Maasai; Are they parasitic on cattle as they keep the animals alive but feed on their blood & milk (15 animals support 1 adult)? A parasite “needs its host & gains the most” Parasites are highly evolved to fill this niche – Loss of movement in adult forms – Multiple developmental stages (to assist transmission) – Redirection of resources to breeding – We will now look at the tapeworm as an example 57 57 Tapeworm Tapeworms have neither gut nor stomach, they just absorb predigested food from the host (us!) Tapeworms can reach up to 25M in length and attach themselves using their head or scolex (right) The mature tapeworm can produce 200K eggs/day And their lifecycle… 58 58 29  6/1/22 59 59 And finally, omnivores An omniverous feeding strategy is probably the most flexible and successful approach adopted by animals Three of the most ubiquitous animal species on earth are omniverous - cockroaches, rats and humans What are the advantages and disadvantages of this feeding strategy and what evolutionary‘baggage’ has it bequeathed us? 60 60 30  6/1/22 Advantages Animals that can eat many different foods can survive in all habitats where food is available As they can be flexible about what they can eat, they can… – Survive when a particular food source becomes scarce – Benefit when a particular food source becomes abundant – Rapidly adapt to changing environmental circumstances (e.g., climate change, urbanisation, farming etc) 61 61 Disadvantages (Costs) If an animal’s dietary variety is constrained, it does not face the problem of deciding what is safe to eat This leads us to what is termed the‘omnivores paradox’ - we can eat many things, but will eating those things provide energy or will they make us sick or kill us? And this is no joke… – Plants and animals can be extremely toxic and large numbers of people are STILL poisoned every year. – Just SOME examples Lathyrsm– Grass pea (10,000+) Konzo (Right) – Cassava (10,000+) Toxic hypoglycemia – Lychees (1000+) Marine neurotoxins – Shellfish, fish (500,000+) – (e.g. Domoic acid – Amnestic shellfish poisoning) 62 62 Lathysm; The Grass pea is such a hardy plant that it often survives res in Africa and a undisclosed population of African's are forced to eat it because there's nothing else. each year over 10,000 people get poisoned from digesting it and it also causes paralysis in the lower limbs. Konzo; can also come from eating the Cassava plant which didn't remove the cyanide in the washing processes. It damages the tissues in their spine and paralyses them. 31 Toxic hypoglycemia; plummets blood sugar levels and kills about 1000 people per year.  6/1/22 Consequences One way to tackle the omnivores paradox is to develop a brain and sensory systems that can… – Detect and avoid foods that are likely to make one sick or die – Learn the safety, nutritional value, and seasonal location of its many different foods – Support behavioural flexibility - hunting, gathering and utilising every feeding opportunity – including learning from others So like the omnivorous rat we… – Tend to avoid bitter tasting foods (poison!) – Tend to avoid foods that look, feel or smell rotten (with humans having evolved a special emotion for this - disgust) – Demonstrate caution to novel foods (neophobia) – Prefer sweet and/or fatty foods that signal ‘energy’ – Show extensive learning capacity relating to the foods we eat And like all animals we… – Tend to maximise energy intake and minimise energy expenditure 63 63 Conclusions In this lecture we have surveyed the many different strategies employed by animals to obtain energy - food These strategies define to a large extent the sort of questions that we might ask about eating behaviour and physiology In omnivores, key questions pertain to – The sensory apparatus (the CNS) that informs what we might eat – How we choose one food over another when so many are available – The control of ingestion - what starts and stops eating Consequently, these will form the topics for the next three sets of lectures 64 64 32