Animal Evolution and Behaviour (Term 1) Flashcards

Question

What are vertebrates?

Answer 1

Vertebrates are animals that have a backbone inside their body. The major groups include fish, amphibians, reptiles, birds and mammals. Invertebrates don't have a backbone. They either have a soft body, like worms and jellyfish, or a hard outer casing covering their body, like spiders and crabs.

Answer 2

The Cambrian explosion happened more than 500 million years ago. It was when most of the major animal groups started to appear in the fossil record, a time of rapid expansion of different forms of life on Earth

Answer 3

According to evolutionary psychologists, patterns of behavior have evolved through natural selection, in the same way that physical characteristics have evolved. Because of natural selection, adaptive behaviors, or behaviors that increase reproductive success, are kept and passed on from one generation to the next. Organisms evolve because they are in an ecological relationship with other organisms of their environment, and because the environment itself influences their evolution via natural selection.

Answer 4

Descent with modification, crucially including adaptation to the environment due to natural selection on heritable variation.

Answer 5

Evolution can operate rapidly, over generational timescales, at the same timescale in which ecological interactions occur (between biological individuals and with their environment). (Evolution can also operate and have effects over very long timescales E.g. in macroevolution.) Therefore, because evolution and ecology can operate on the same timescale, ecology could affect evolution and evolution could affect ecology. Interactions in both directions, between ecology and evolution (and vice versa), may occur in feedback loops.

Answer 6

In the mid 20th century new insights into the mechanism of genetic inheritance (based on genes) allowed the integration of Darwinian ideas of evolution with new ideas principally Mendelian genetics. The Modern Synthesis also integrated other fields such as palaeontology. The modern synthesis includes much of the evolutionary theory we now use in practice. E.g. The Hardy-Weinberg equation: using gene frequencies to tell if evolution is occurring in a population. Key figures in the Modern Synthesis included Fisher, Haldane, Dobzhansky, Wright, Ford and others.

Answer 7

Sensing the environment is essential for many aspects of the lives of animals The most common sensory systems are; mechanical, visual, auditory or olfactory/gustatory Sensing has a physiological basis, encoded in genes, and usually requires (or leads to) specific behaviours Simple stimuli can underpin complex interactions

Answer 8

A behaviour is an action carried out by muscles under the control of the nervous system All of animal physiology contributes to behaviour, and behaviour influences all physiology The ability to sense and react evolved billions of years ago in prokaryotes Often, reactions are to environmental stimuli Enhanced survival and reproductive fitness Simple recognition and reponse circuits led, ultimately, to complex nervous systems and behaviours – like choosing to study at the University of Essex!!

Answer 9

Synapses are junctions between neurons and other cells Most synapses are chemical synapses When an action potential depolarises the plasma membrane at the synapse, calcium channels open The increasing intracellular Ca2+ level causes the release of neurotransmitter The neurotransmitter binds to a receptor on the postsynaptic cell

Answer 10

Behaviour requires animals to sense their environment Stimuli and responses are diverse, but signal detection and transmission always happen the same way Sensory neurons transmit electrical signals by ion transport across membranes Neurons form nerves that form nervous systems Complex organisms  complex nervous systems  complex (learned) behaviours

Answer 11

Tinbergen kept three-spined sticklebacks (Gasterosteus aculeatus) Males are very territorial and will attack other males Male fish do not attack female fish Hypothesis: red colouration is the stimulus for aggression (proximate cause) Territorial response is a “Fixed Action Pattern” Sequence of unlearned acts linked to stimulus Once initiated, continue until completed Trigger is external, is called a “Sign Stimulus”

Answer 12

Psychological systems and processes Carried out by muscles under nerve control Behaviour can be for reproduction, defence, foraging For homeostasis, adjusting conditions Feedback from and to Physiology

Answer 13

Learning is “modification of behaviour as a result of experiences” Learning capacity is dependent on nervous system organisation Learning is formation of memories = changes in neural connections Challenge to explore how nature (genes) and nurture (environment) combine for learning In many species, bonding with others is important for survival In infants – imprinting to others occurs only during the “sensitive period” In Gulls – 1-2 day period of mutual imprinting of parent to offspring and offspring to parent

Answer 14

What is the stimulus, what is the physiological mechanism that mediates response? How does experience/development mediate response? How does behaviour aid survival & reproduction What is the evolutionary history of behaviour?

Answer 15

- Different forms of learning - Behaviour can be modified by learning, development, physiology - Sensitive periods - Behaviour can evolve through optimality; i.e. decision making evolves - Behaviour can be passed on by learning, as well as being genetically inherited - Sometimes a single allele – sometimes more complex

Answer 16

Competition for access to mates and successful reproduction drives sexual selection (inc. sexual conflict later in course). Parental care and certainty of paternity drives mating system structure Many mate choice systems promote pre- (leks and female choice; male territory fighting), during (mallard mating flights) or post- copulatory (multiple mating and sperm competition) competition between males Competition can lead to selection for variant advantage – frequency dependent selection – leads to a game (e.g. Game Theory) Male polymorphisms can arise - rare phenotype advantage can occur

Answer 17

Three general mating systems, all involving innate as opposed to learned behaviors, are seen in animal populations: monogamous (monogamy), polygynous (polygyny), and polyandrous (polyandry). In monogamous systems, one male and one female are paired for at least one breeding season.

Answer 18

Natural selection favours behavior that maximizes an individual’s survival and reproduction These behaviors are (often) selfish Some animals behave in ways that reduce their individual fitness but (appear to) increase the fitness of others This kind of behavior is called altruism

Answer 19

Direct fitness is fitness gained through personal reproduction Indirect fitness is fitness achieved by helping nondescendant kin survive and reproduce The evolution of altruistic behavior can be explained by inclusive fitness Inclusive fitness is the total effect an individual has on proliferating its genes by producing offspring and helping close relatives produce offspring

Answer 20

Altruistic behavior toward unrelated individuals can be adaptive if the aided individual returns the favor in the future This type of altruism is called reciprocal altruism Reciprocal altruism is limited to species with stable social groups where individuals meet repeatedly and cheaters (who don’t reciprocate) are punished This strategy has the following rules - Individuals always cooperate on first encounter - An individual treats another the same way it was treated the last time they met - That is, individuals will always cooperate, unless their opponent cheated them the last time they met

Answer 21

Intragroup hierarchy – competition for food – remember ideal free distributions! Lost mating opportunities – competition Increased detection Paternal certainty Brood parasitism Parasitism & disease transmission Rarely, spiteful behaviour

Answer 22

Shared responsibilities – foraging more successful Inclusive fitness – reduced cost Finding a mate Protection Other fitness benefits

Answer 23

The scientific study of the interactions between organisms and their environment that determines the distribution and abundance of organisms

Answer 24

Organismal ecology studies how an organism’s structure, physiology, and (for animals) behavior meet environmental challenges

Answer 25

Ecology is the science of abundance and distributions Population ecology is the science of abundance and distribution of a single species Individuals of a population can be spread throughout their range in different ways and for a variety of reasons Population dynamics (change in density over time) is the sum of four factors/processes/parameters

Answer 26

Demography is the study of the vital statistics of populations and how they change over time.”

Answer 27

R0= Number of daughters in generation t+1 divided by Number of females in generation t

Answer 28

It is the average number of daughters born to each female if the cohort lives its entire reproductive life according to the fertility and survival schedule in its life table

Answer 29

R0 and r ARE NOT THE SAME R0 is net reproduction rate (current population) r is Intrinsic per capita capacity for increase (maximum potential growth) Growth can be regulated and/or limited Regulation is Density Dependent Other mortality & limitation are density independent IN THEORY – regulation results in “equilibrium” or noisy equilibrium dynamics Regulation is real – but equilibriums are rare or short lived

Answer 30

The traits that affect reproduction and survival make up its life history Life history traits … - Size at birth - Growth rate - Age and size at sexual maturity - Number, size, and sex of offspring - Schedule of reproduction - Age/stage/size-specific rates of survival - Lifespan

Answer 31

Trade off between number of offspring and parental survival Trade off between number of offspring and size of offspring Trade off between number of offspring and provisioning (e.g. . parental care)

Answer 32

- Small size - Many small offspring - Little energy used per offspring - Early maturity - Short life expectancy - Semelparity - Type 3 survival curve

Answer 33

- Large size - Few large offspring - Much energy used per offspring - Late maturity and often parental care - Long life expectancy - Iteroparity - Type 1 or 2 survival curve

Answer 34

Intraspecific competition is an interaction in population ecology, whereby members of the same species compete for limited resources. This leads to a reduction in fitness for both individuals, but the more fit individual survives and is able to reproduce.

Answer 35

In exploitation competition, the competition between organisms is indirect. It is in contrast to the interference competition wherein the interaction between competing organisms is direct.

Answer 36

Contest competition is often the result of aggressive social domains, including hierarchies or social chains. Conversely, scramble competition is what occurs by accident when competitors naturally want the same resources.

Answer 37

Interspecific competition might drive the evolution of ecological niches and result in pairs of formerly competing species segregating along ecological gradients following a process of character displacement.

Answer 38

Individuals of different species compete for a resource that limits growth, survival or reproduction -/- interaction Can be experienced through individuals of similar size – or a more asymmetric interaction

Answer 39

Two species competing for the same limiting resources cannot coexist permanently in the same space leads to competitive exclusion principle, Hardin (1960)

Answer 40

Competition between members of different species is Interspecific competition Can be asymmetric, interference, exploitation etc – just like intraspecific Species that have fully overlapped requirements (or methods to obtain them) share the same niche and cannot coexist Niches can differ a little – or a lot An animal has a fundamental and a realised niche - affects distributions This difference results in plastic or evolutionary changes in animals that lead to coexistence and diversity, new forms Consequences of strong competition include niche partitioning and character displacement Competition can be difficult to detect in the wild – always a Ghost of competition past Competition easier to detect in seasonal peaks or non-native introductions

Answer 41

Numerical response – the response of a predator population to changes in prey density (via predator reproduction). Will the density of predators change in response to prey density (through predator reproduction)? Aggregative response – density of predators changes in area through movement to patches of high prey abundance Functional response - the response of the average predator to the density of the prey. Does a predator eat more or less prey as prey density changes? Developmental response – functional response changes as individuals grow

Answer 42

Carnivory, Herbivory, parasitism and mutualism.

Answer 43

Pathogens can influence community structure Coral reefs “white band disease” 1. Disease kills corrals that provide habitat for lobsters, snappers and other fish 2. Dead corral are overgrown by algae 3. Surgeon fish and other herbivore fish dominate the fish community 4. Diversity plummets

Answer 44

Constant battle between disease organisms and host, and predators and prey, coevolution, arms race Adaptations to escape, adaptations to exploit better Everything is adapting and evolving but staying in the same place – Red Queen Evolution of virulence countered by genetic diversity of host Prey defences - Colourations, mimicry, mechanical, cypsis… Brood parasitism

Answer 45

supergroup Excavata Many of the protist species classified into the supergroup Excavata are asymmetrical, single-celled organisms with a feeding groove “excavated” from one side. This supergroup includes heterotrophic predators, photosynthetic species, and parasites. Its subgroups are the diplomonads, parabasalids, and euglenozoans

Answer 46

Diplomonads are small cells, usually around 10 μm in length and often less. With the exception of the enteromonad organisms (see 'Systematics'), diplomonads have a characteristic 'doubled' organization. Each cell has two identical-sized nuclei located alongside each other in the anterior half of the cell

Answer 47

Parabasalids are characterized by a semi-functional mitochondria referred to as a hydrogenosome; they are comprised of parasitic protists, such as Trichomonas vaginalis. Euglenozoans can be classified as mixotrophs, heterotrophs, autotrophs, and parasites; they are defined by their use of flagella for movement

Answer 48

Euglenoids move through their aquatic habitats using two long flagella that guide them toward light sources sensed by a primitive ocular organ called an eyespot.

Answer 49

Animals can either hunt at different times of day to one another. Or they can hunt in groups and increase their chances of success.

Answer 50

Advantages: Safety/Protection Can spot danger quickly Obtain larger amounts of prey Disadvantages: Spreading diseases Increased competition among the group for things such as foods/ mates.

Answer 51

r species are animals that put little effort into raising many offspring. R0 is the basic reproduction value which indicates the number of secondary cases in susceptible population from one diseased animal.

Answer 52

Natural selection is the process where animals evolve very slowly overtime to better suit their environment and increase chances of survival. Moreover to also pass on the new phenotype to newer generations. Variation. Organisms (within populations) exhibit individual variation in appearance and behavior. These variations may involve body size, hair color, facial markings, voice properties, or number of offspring. On the other hand, some traits show little to no variation among individuals—for example, number of eyes in vertebrates. Inheritance. Some traits are consistently passed on from parent to offspring. Such traits are heritable, whereas other traits are strongly influenced by environmental conditions and show weak heritability. High rate of population growth. Most populations have more offspring each year than local resources can support leading to a struggle for resources. Each generation experiences substantial mortality. Differential survival and reproduction. Individuals possessing traits well suited for the struggle for local resources will contribute more offspring to the next generation.

Answer 53

First, phylogenetic classification tells you something important about the organism: its evolutionary history. Second, phylogenetic classification does not attempt to “rank” organisms. Linnaean classification “ranks” groups of organisms artificially into kingdoms, phyla, orders, etc. Phylogenetics shows a longer history, It also has higher degrees of biological diversity and differentiation. Phylogenetic: Shows common ancestors, shows time sequence, no language specification. Linnaean: Shows hierarchy classification, no indications of time or evolution, organised using taxon, in Latin. Therefore used for different situation. However I believe Phylogenetics has higher utility due to using a phylogenetic tree which can be very useful.

Answer 54

Generalist species can feed on a wide variety of things and thrive in various environments such as racoons. Specialist species eat a limited diet and occupy a much narrower niche such as koalas which only feed on the leaves of eucalyptus trees.

Answer 55

Its where the predator switches to eat the most common or abundant prey to not endanger other prey species.

Answer 56

Exploitative: A form of competition wherein organisms indirectly compete with other organisms for resources by exploiting resources to limit the resources availability to other organisms. Interference: The competition that occurs when two organisms demand the same resource and that resource is in short supply, and one of the organisms denies its competitor access to the resource.

Answer 57

Optimal foraging assumes that natural selection has resulted in foraging behaviour that maximizes fitness, while taking into account the dependence of energy intake rate on the forager's ability to detect, capture, and handle each prey item.

Answer 58

A dorsal supporting rod and a post-anal tail.

Answer 59

It is the study of population dynamics

Answer 60

Natural selection is a mechanism of evolution. Organisms that are more adapted to their environment are more likely to survive and pass on the genes that aided their success. This process causes species to change and diverge over time.

Answer 61

The Red Queen hypothesis was coined in evolutionary biology to explain that a species must adapt and evolve not just for reproductive advantage, but also for survival because competing organisms also are evolving.

Answer 62

An individual's reproductive value is the expected number of copies of each of its genes that is passed on to distant generations conditional on its pedigree. Depending on what traits the offspring inherits it will have knock on affects for species in time since they will diverge more and more over time. Which will show an affect on the life histories.

Answer 63

Living in groups provides animals with many benefits. A large group of animals is less likely to be bothered by predators, there are more females to care for and protect the young, and more members to look for food sources. Working together provides them with more opportunities for survival than living alone does.

Answer 64

Ctenophores have true, differentiated tissues and organs, including muscles and a nervous system (a nerve net). Generally classified as diploblastic (with embryonic ectoderm and endoderm). Mesoglea is a jelly layer that lies between their layers of metabolically active layers. Traditionally ctenophores are classified as radially symmetrical.

Answer 65

Endoderm: Inner linings e.g. digestive tract (i.e. guts) and organs derived from it (e.g. lungs) as well as secretory organs (liver, pancreas, thyroid, thymus…). Ectoderm: Outer linings e.g. epidermis and nervous system, as well as hair, cornea, tooth enamel, etc. Mesoderm: Middle layer forming e.g. coelom, notochord in chordates, muscles, bone/cartilage, circulatory, spleen, kidney, reproductive organs, etc.

Answer 66

Molecular clocks allow estimation of ages of divergences based on differences in DNA and estimates of the rate of DNA substitution e.g. via calibration to known fossils. Molecular clock dates (e.g. Erwin 2009) place the origin of animals and major animal groups in the precambrian Neoproterozoic Era (1000-541 Mya). E.g. The divergence of animals from choanoflagellates is dated to 800 Mya. However, molecular clock date estimates for animal divergences often predate the appearance of the animal groups as ‘body fossils’. This could suggest there is a significant precambrian fossil record still to discover.

Answer 67

``` Finding food Detecting Predator Object Avoidance Finding a mate Controlling rhythms Navigation Territories ```

Answer 68

A behaviour is an action carried out by muscles under the control of the nervous system All of animal physiology contributes to behaviour, and behaviour influences all physiology The ability to sense and react evolved billions of years ago in prokaryotes Often, reactions are to environmental stimuli Enhanced survival and reproductive fitness Simple recognition and response circuits led, ultimately, to complex nervous systems and behaviours Psychological systems and processes Carried out by muscles under nerve control Behaviour can be for reproduction, defence, foraging For homeostasis, adjusting conditions Feedback from and to Physiology

Answer 69

Nikko proposed that discrete sensory inputs stimulate simple and complex behaviours. To understand behaviour: What is the stimulus, what is the physiological mechanism that mediates response? How does experience/development mediate response? How does behaviour aid survival & reproduction What is the evolutionary history of behaviour?

Answer 70

Chemical odours and tastes that elicit a response Common in mammals and insects, but also in aquatic environment Most common in courtship, but also in defence and alarm Can be very long range in bees – inhibit ovary development in workers Alarm response in fishes

Answer 71

Territorial response is a “Fixed Action Pattern” Sequence of unlearned acts linked to stimulus Once initiated, continue until completed Trigger is external, is called a “Sign Stimulus”

Answer 72

Developmentally “fixed” behaviours are innate – instinctive 2nd Question investigates role of experience Learning can affect behaviour as animal grows Some new, some developed… Can link to ontogeny/physiology

Answer 73

Learning is “modification of behaviour as a result of experiences” Learning capacity is dependent on nervous system organisation Learning is formation of memories = changes in neural connections Challenge to explore how nature (genes) and nurture (environment) combine for learning In many species, bonding with others is important for survival In infants – imprinting to others occurs only during the “sensitive period” In Gulls – 1-2 day period of mutual imprinting of parent to offspring and offspring to parent

Answer 74

If foraging optimally a duck would maximise food intake relative to the risks: - ---Not enough food per individual - ---Differences in competitive ability of ducks An informed and achievable decision: - Assumes duck knows quality of different patches - Assumes duck can move freely between patches - Assumes all individuals are competitively equal Competitive abilities can be assessed: - Some species can take dominance into account - Coho salmon IDF if include competitive weights

Answer 75

Most blackcaps (birds) that breed in Germany winter in Africa, but some winter in Britain Under laboratory conditions, each migratory population exhibits different migratory behaviors The migratory behaviors reflect genetic differences between populations

Answer 76

Learning allows behaviour to adapt following experiences and during growth Leads to differences in behaviour – unlike Fixed Action Patterns where all are same Differences between individuals are the foundation of evolution Behaviour can evolve through balancing risks and reward This can be allele/genetic based or more complex selection on competitive ability/cognition (e.g. Optimal Foraging)

Answer 77

Mating behavior and mate choice play a major role in determining reproductive success Mating behavior includes seeking or attracting mates, choosing among potential mates, competing for mates, and caring for offspring Mating relationships define a number of distinct mating systems. In some species, mating is promiscuous, with no strong pair-bonds Other species form monogamous relationships where one male mates with one female Males and females with monogamous mating systems have similar external morphologies

Answer 78

Certainty of paternity also influences parental care and mating behavior Females can be certain that eggs laid or young born contain her genes Paternal certainty is relatively low in species with internal fertilization because mating and birth are separated over time Certainty of paternity is much higher when egg laying and mating occur together, as in external fertilization In species with external fertilization, parental care is at least as likely to be by males as by females

Answer 79

Sexual dimorphism results from sexual selection Why do long eye stalks, or horns or fancy colouration indicate fitness? Sexual selection is a form of natural selection in which differences in reproductive success result from differences in mating success. In intersexual selection, members of one sex choose mates on the basis of certain traits Intrasexual selection involves competition between members of the same sex for mates

Answer 80

Female choice is a type of intersexual selection Females can drive sexual selection by choosing males with specific behaviors or features of anatomy Ornaments, such as long eyestalks, often correlate with health and vitality (=good genes; assumes honest signal) Mate choice can also be influenced by imprinting For example, female zebra finch chicks show no preference for male ornamentation when raised by fathers without ornamentation Female chicks raised by fathers with artificial ornamentation (red feather) preferred ornamented males as mates

Answer 81

Male competition for mates is a source of intrasexual competition It can reduce variation among males through the exclusion of subordinates Can involve agonistic behavior, an often ritualized contest To achieve reduced competition at mating – strong selection on behaviour and morphology

Answer 82

To analyse Tinbergen’s 3rd question we can apply Game Theory The fitness of a particular behavioral phenotype can depend on others in the population Game theory evaluates alternative strategies in situations where the outcome depends on the strategies of all individuals involved For example, each side-blotched lizard has a blue, orange, or yellow throat; each associated with a specific strategy for obtaining mates: - Orange-throat males are the most aggressive and defend large territories with many females - Blue-throats defend small territories with fewer females - Yellow-throats are non-territorial, mimic females, and use “sneaky” strategies to mate

Answer 83

Like rock-paper-scissors, each strategy will outcompete one strategy but be outcompeted by the other strategy Game theory……. The success of each strategy depends on the frequency of all of the strategies; this drives frequency-dependent selection Drives male polymorphism in behaviour and morphology

Answer 84

Competition for access to mates and successful reproduction drives sexual selection (inc. sexual conflict later in course). 3 main mating systems, monogamy, polygyny and polyandry Parental care and certainty of paternity drives mating system structure Many mate choice systems promote pre- (leks and female choice; male territory fighting), during (mallard mating flights) or post- copulatory (multiple mating and sperm competition) competition between males Competition can lead to selection for variant advantage – frequency dependent selection – leads to a game (e.g. Game Theory) Male polymorphisms can arise - rare phenotype advantage can occur

Answer 85

Natural selection favours behavior that maximizes an individual’s survival and reproduction These behaviors are (often) selfish Some animals behave in ways that reduce their individual fitness but (appear to) increase the fitness of others This kind of behavior is called altruism

Answer 86

Direct fitness is fitness gained through personal reproduction Indirect fitness is fitness achieved by helping nondescendant kin survive and reproduce The evolution of altruistic behavior can be explained by inclusive fitness Inclusive fitness is the total effect an individual has on proliferating its genes by producing offspring and helping close relatives produce offspring

Answer 87

Before any of this was understood, V. C. Wynne-Edwards proposed that natural selection operates at the level of the group/population/species He based this on the belief that groups containing altruistic individuals are more likely to survive than those without Superficially explains why a honey bee might die to save the colony George C. Williams countered that individual selection could just as easily explain the evolution of an altruistic trait… …and that selection of individuals has a stronger evolutionary effect than selection based on differences between groups We now know that it comes down to genes, and probabilities

Answer 88

William (Bill) Hamilton proposed a quantitative measure for predicting when natural selection would favour altruistic acts among related individuals There are three key variables in an altruistic act - Benefit to the recipient (B) - Cost to the altruist (C) - Coefficient of relatedness (the fraction of genes that, on average, are shared, r) Natural selection favors altruism when: rB > C This inequality is called Hamilton’s rule

Answer 89

Altruistic behavior toward unrelated individuals can be adaptive if the aided individual returns the favor in the future This type of altruism is called reciprocal altruism Reciprocal altruism is limited to species with stable social groups where individuals meet repeatedly and cheaters (who don’t reciprocate) are punished This strategy has the following rules - Individuals always cooperate on first encounter - An individual treats another the same way it was treated the last time they met That is, individuals will always cooperate, unless their opponent cheated them the last time they met

Answer 90

R0 and r ARE NOT THE SAME R0 is net reproduction rate (current population) r is Intrinsic per capita capacity for increase (maximum potential growth) Growth can be regulated and/or limited Regulation is Density Dependent Other mortality & limitation are density independent IN THEORY – regulation results in “equilibrium” or noisy equilibrium dynamics Regulation is real – but equilibriums are rare or short lived

Answer 91

The traits that affect reproduction and survival make up its life history Life history traits … - Size at birth - Growth rate - Age and size at sexual maturity - Number, size, and sex of offspring - Schedule of reproduction - Age/stage/size-specific rates of survival - Lifespan

Answer 92

Life history – three main variables of reproduction -When reproduction begins -How often reproduction occurs -How many offspring per reproductive event

Answer 93

Semelparity – Big Bang – or One Shot reproduction -Many small offspring Iteroparity – Repeated reproduction -Fewer larger offspring

Answer 94

Lab – e.g. microcosms: - Replication easy - Simple through to communities of many species - Easily controlled starting population numbers - Easy to control other factors that could affect things – e.g. temperature - Often low cost - Often over short time periods Field studies: - Uncontrolled conditions e.g. temperature and rainfall - But that is realistic - Can be of large scale things impossible in the lab - More expensive - Can be over longer time periods

Answer 95

In simple habitats predators can drive prey extinct Complexity/Refuges can promote prey Space/Time can provide refuges

Answer 96

As predator populations increase, they put greater strain on the prey populations and act as a top-down control, pushing them toward a state of decline. Thus both availability of resources and predation pressure affect the size of prey populations. Predators affect individual growth rates of surviving prey in two conflicting ways. First, predation acts to increase growth rate by thinning the density of prey population, which releases survivors from competition. At the same time, predators intimidate prey into decreasing their feeding activity and increasing refuge use, causing prey to grow more slowly. Both processes are known to affect individual growth rates in many systems, but their relative importances and interactive effects have not been measured.

Animal Evolution and Behaviour (Term 1) Flashcards

(120 cards)