Module 3

Question 1

Explore some of the recent and early ideas about defining characteristics of life.

Answer 1

• Feeding
• Assimilation (digestion)
• Growth
• Maintenance
• Development (maturation)
• Reproduction

Question 2

Explore the ways organisms fight against the idea of disorder.

Answer 2

Homeostasis:

• The way organisms keep themselves order despite the tendency of everything towards disorder; organisms need to receive, store, and respond to information for homeostasis to occur
• Information encoding in genes (aperiodic crystals/DNA in which information is stored leads to orderly behaviour of organisms)
• What is life?
• Exchange of energy, matter, and information
• Individuals are special – goal-directed
• Maxwell’s demon:
• Information is about what you know, and entropy is about what you don’t know
• Entropy:
• Heat moves randomly
• Work is movement of molecules going in the same direction (ordered)

Question 3

Describe the different scales in biology and why the individual is special in terms of metabolism.

Answer 3

Metabolism:

• Scale/levels in biology
• Nanometre – respect space; DNA, little proton pumps
• Micrometre – organelles in cells
• Micrometres to metres – organisms, individuals
• Populations – mm to km
• Community – mm to km
• Ecosystem – mm to km

Question 4

Compare metabolic rate and how it changes with temperature and size.

Answer 4

Metabolic rate:
- The amount of energy your body uses to maintain itself and is made up of 5 main components:
- -> Basal metabolic rate (BMR): amount of energy the body uses when at rest for endotherms
- * Isn’t moving
* Isn’t digesting
* Is in a thermoneutral zone
* Is in its inactive phase
* Is an adult
* Is not reproducing
- -> Thermic effect of food: the energy the body uses to digest, store, transport food and drinks
–> energy used during physical activity

–> Standard metabolic rate (ectothermic animals):
- The minimum energy needed for sel-maintanence for ectotherms
- Ectotherm: relies on external heat sources to regulate its body temperature
* Isn’t moving
* Isn’t digesting
* Is at a known temperature
* Is in its inactive phase
* Is an adult
* Isn’t reproducing
- Resting metabolism:
* Isn’t moving
* Isn’t digesting
* Is in its thermoneutral zone (it isn’t feeling cold)

–> Field metabolic rate:
- Metabolic rate measured for an organism behaving naturally in the wild, incorporates all the energy requirements that the organism has (not just resting)
* Doubly labelled water – where the organism is captured and injected with heavy water (water with an extra neutron) so the water can be trapped and can capture animal again after some time and take a blood sample to see how much of labelled water has been diluted, giving an indirect measure of the amount of energy it has consumed

• Temperature and metabolic rate:
• Homeothermic: constant temperature
• Endotherm: generates heat to raise body temperature above ambient
• Temperature increases metabolic rate
• The metabolic web:

Ways metabolic rate can be measured:
- Heat production: direct ‘calorimetry’
- Gas measurement: Indirect calorimetry
(Influenced by muscular work, food consumption, temperature)

Question 5

Summarise the temperature response curve.

Compare temperature responses of endotherms and endotherms as well as some possible physiological effects of climate warming.

Answer 5

• Thermoregulation is a homeostatic process that maintains a steady internal body temperature despite changes in external conditions
• The metabolic niche:
• Niche of the animal – set of environmental requirements that they have that are suitable to allow the population to grow (temperature, food, water, pH, biotic environment)
• Temperature:
   As body temperature increases, metabolic rate increases
   Temperature response curves:

 Can use temperature response curves to predict the distribution of organisms in certain regions over others (e.g. Warmer regions may tend to have a greater proportion of certain organisms)
 Organisms need to spend enough time in the optimal temperature zone to be able to successfully grow, develop and reproduce
* Temperature and ectothermy:
 ‘cold-blooded’ – not a very accurate term
 Poikilothermic – variable temperature
 Ectothermic – receives heat from outside (cannot generate a huge amount of heat internally)
 Temperature tolerance data is important as it give information on the optimal temperatures at which enzymes and cell membranes (fluidity), protein folding etc. functions in certain organisms
 
* Temperature and endothermy:
 ‘warm-blooded’ – not very accurate term
 Homeothermic – constant temperature
 Endothermic – generates heat internally

• Behavioural thermoregulation:
   Organisms moving into the shade to cool, climbing tree etc.
   Climate change and global warming will impact the temperature response curves of “specialist” organisms (organisms with a narrower range of temperatures which they can survive and regulate in) to a greater level as they have a narrow range of limits which they can survive in, e.g. tropical species

Question 6

Explore the different sensory modalities or channels that are used to convey information.

Use examples to illustrate how signals and cues provide organisms with information about their constantly changing environment.

Answer 6

• Signals and cues provide organisms with information about their constantly changing environment
• Organisms require information about their local environment:
• Information provided by the presence/absence of signals and cues
• The signal/cue must be reliable and readily discernible from background noise
• The environment of an organism constantly changes:
• Abiotic changes – temperature, humidity, sunlight and (altitude, longitude, and substrate for mobile organisms)
• Biotic changes – temporal and spatial variation in the abundance of food, competitors, natural enemies (predators, parasites, pathogens) and reproductive partners
• Cues for predators:
• Distance between broken and intact egg (some birds hence remove broken eggshell after chick is born to reduce predation)
• Singing the same birdsong for recognition and conveying information
• Selection must favour the evolution of the sensory mechanisms that allow the signal or cue to be detected
• Producing pheromones (chemicals/odours) to transmit information
• Sensory modalities:
• Information is conveyed through diverse sensory modalities or channels
• Chemical modality (olfaction):
   Must be a physical interaction between odour and receptor
• Electrical modality:
   Works well in aquatic environments because electricity is more easily transported through water and air
   E.g. a shark can detect the location of a fish even when it is constrained in the ‘agar chamber’ in sand
• Visual (Light) modality:
   Visual acuity (the ability to see) varies across species, and may depend upon eye size
   E.g. the ability to detect a signal (a natural decoration on a spider’s web) varies with distance and species
• Magnetic modality (magnetoreception):
   Bacteria and many animals detect and respond to the magnetic field, allowing them to orient over long (i.e. migration) and short (i.e. homing) distances
• Mechanical modality:
   Web building spiders use vibrations, transmitted along the flexible silk, to detect the location and size of prey that are arrested by the web
• Sound modality:
   Sound frequency/echolocation: objects in space are located by directing sounds at them and detecting the echoes, the longer the time interval until the echo is detected, the further away the object
• Signal – any act or structure that influences the behaviour of other organisms (receivers), and which evolved specifically because of that effect, selection will favour greater distinctiveness in the signal and greater ability of the receiver to detect it
• Cue – an incidental source of information that may influence the behaviour of a receiver, despite not having evolved under selection for that function, selection may favour greater detection abilities in the receiver, but won’t act on the cue, unless it disadvantages the source of the cue
• Signals are effective only if they are detected:
   Signals and the information they provide may not reach their intended receiver because they attenuate as they travel through the environment (it is more difficult to discern colour patterns or hear sounds the further from the source)
   Background noise can affect signal detection
   Signal strategy – night coloration reveals toxicity and this reduces likelihood of predation
   Signal efficacy – same information, different impact
• Source of ‘information’ allowing animals to behave:
• Innate:
   A behaviour that is performed the first time an animal encounters the cue or signal appropriate for that behaviour
• Learned:
   A behaviour that is modified as a result of the animal’s experience of its environment

Question 7

Compare and contrast the development of signals and cues in different organisms.

Question 8

Describe different ways in which organisms exploit information in the environment (for example eavesdropping, camouflage and mimicry).

Answer 8

What is being signalled?
- Eavesdropping
* Signalling isn’t just physiologically costly but can reveal the location of the signaller, thereby providing a cue for a natural enemy
* Most eavesdropping Is of an intra-specific signal – released and detected by members of the same species
- Costs to signalling
* Physiological: drain on resources during growth (e.g. visual signals like feathers or organs for bioluminescence), or during immediate production of signal (movement or making sounds and vibrations)
* Exploitation: signals (or cues) may be intercepted by an untended receiver (predator or parasite)
- Camouflage and mimicry
* Organisms exploit information in the environment, through camouflage and mimicry, to avoid or enhance detection
* Camouflage reduces the likelihood that an organism will be detected or recognised
* Masquerade:
 A type of camouflage that prevents recognition by resembling an uninteresting or unimportant object, like a leaf or stick
* Motion masquerade:
 body movement improves crypsis against a moving background, and thus reduces the likelihood of detection, individuals will start swaying when they detect changes in wind pressure, e.g. the spiny tick insect often sways when hanging from a branch
* Aggressive mimicry:
 E.g. frogfish have a ‘lure’ that attracts prey (fish) by mimicking worms, small shrimps, or fish
 E.g. the surface odour of a salticid spider resembles that of green tree ants, allowing the spider to gain access to the nest

• Brood parasitism:
   Where a female of one species lays her eggs in the nests of another species, who raise the ‘parasitic’ chick, avoiding the costs of raising chicks, while the cost to the host includes an energetically costly loss of reproductive output

Question 9

Discuss the role of the relationship between the signaller and receiver in the evolution of communication, with an emphasis on antagonistic coevolutionary processes.

Answer 9

Coevolution and arms races
* The evolution of communication may involve antagonistic coevolutionary processes, depending upon the relationship between signaller and receiver
* Coevolution: a process involving pairs of species (or lineages) whereby changes in the traits of individuals of one species (or lineage) causes reciprocal changes in the other species (or lineage) over evolutionary time
* Arms races: antagonistic interactions may lead to reciprocal evolutionary change; while both predator and prey improve their offensive and defensive adaptations, there is little change in their net advantage

Question 10

Explain how information can be conveyed from one individual to another and the conflicts that may arise from this.

Answer 10

• Reproduction and information
• An organism requires information to develop from egg to adult, and reproduction allows that information to be conveyed from one individual to another individual
• Genotype – a source of information that together with the environment determines the phenotype of an individual
• Asexual organisms – information is transmitted directly and perfectly from female to female
   Facultative parthenogenesis: females can produce viable eggs irrespective of whether mating has taken place
   Hermaphroditism: organisms have complete or partial reproductive organs and produce gametes normally associated with both male and female sexes
• Sexual reproduction – results in the transfer of slightly different information because it derives from females and males
   Asexual females can produce twice as many childbearing offspring (females) as sexual females, so natural selection might be expected to favour asexual reproduction
   Polyandry: mating with more than one male (polyandry is the best outcome for females whereas polygyny is the best outcome for males)
   Male adaptations to polyandry: Sphragis – dried seminal fluid that covers the female genital opening, preventing other males from mating, interfering with female signalling
   External fertilisation – requires sperm and eggs to find each other
   Internal fertilisation – requires sperm and egg carrying individuals to find each other
   Signals, indicating location and receptivity, are required to bring the gametes together
   Conflicts over choice of partner and number of partners
• Sexual selection – competition between members of one sex (typically males) for reproductive opportunities with the other sex (typically females), mate choice and male-male competition are both underlying mechanisms of sexual selection (both involve signalling)
• Bet hedging against environmental variation
   Asexual species are more common in agricultural habitats that are typically homogenous
   Perhaps sexual reproduction provides advantages in spatially and temporally variable environments
• A signalling explanation why gametes (sperm and eggs) are dimorphic
   Gametes communication through ligand and receptor molecules
   The ligand can be either membrane bound or released in the local environment
   When the interacting cells produce ligand and receptor symmetrically, the ligand will bind to receptors on its own membrane as well as those on the other cell
   This may impair intracellular signalling
   Producing the ligand and receptor asymmetrically resolves this issue
   Dimorphic – occurring in/representing two distinct forms
• Pheromone detection and receptor organ morphology
   Theory: by releasing small quantities of sex pheromone, females attract males with larger and higher quality antennae

Question 11

Identify reproduction requires care and how parental care impacts organisms.

Answer 11

• Reproduction requires care
• Parental care, the provision of nutrients or safety from the elements and natural elements, ensures the embryo can develop and reach sexual maturity, and thus transfer the ‘genetic information’ to the next generation. Parental care can be provided by individuals other than the parents.
• Eusocial insects – extraordinarily cooperative care
   Cooperative care of young: involving more individuals than just the mother
   Sterile castes: help in nest maintenance and raising offspring, but cannot themselves reproduce
   Overlapping generations: such that mother, adult offspring and larval offspring are alive at the same time