Neurobiology and Behaviour

Mohira AshurovaE

E 6.1

There are three types of honey bees with different tasks.

Queen has to lay eggs

Worker bees have to maintain the colonies

Drone bees do not do much for the survival of the colony, but if they do mate with the virgin queen bees then they spread genes to the new colonies.

Worker bees eject drones at the end of the season, when

virgin bees become available.

E 6.1

African Elephants Control: Matriarch female is the eldest of the

female elephants and the nest oldest elephant takes over when the current matriarch dies.

Kinship unit: group of related families remaining in the close proximity to each other. Family groups divide around 20-22 individuals to form new families. Males in the herd are expelled around the age of 12-13

E 6.2 E 6.3

In the case of social animals especially colonies, most of the individuals have very similar dna so these genes are still getting passed down even if they aren’t themselves reproducing. So these animals will sacrifice themselves for the greater good of their very close relatives.

6.3 Altruistic behavior is common through the animal kingdom, particularly in species with complies social structure. For example, vampire bats regularly regurgitate blood and donate it to other members of their group who have failed to feed that night, ensuring they do not starve. In numerous bird species, a breeding par receives help in raising its young from other helper birds, who protect the nest from predators and help to feed the fledglings.

Vervet monkeys give alarm calls to warn other monkeys of the presence of predators, even though in doing so they attract attention to themselves, increasing their personal chance of their attacked.

E 6.4 Foraging is finding food.

All organisms need to find food to survive and reproduce.

Natural selection will favour strategies that minimise the costs of the search and maximise the benefits.

Foraging Theory suggests that the food choice of the animal will maximise the energy obtained.

The food choice is a consequence of:

1. Cost = energy used to pursue, capture and consume the food.

2. Benefit = energy from the individual food item.

Predator Blue Gill Sunfish Prey:

Water fleas (Daphnia) Studies by Werner and Hall tested optimal foraging strategies in the Bluegill Sunfish (Lepomis macrochirus).

The hypothesis to be tested is that: Blue gill fish will, if the prey availability is altered, change their feeding choices to maximise the energy benefits and reduce costs

Phase 1: Cost benefit analysis

The costs and benefits from the feeding are calculated including Energy content of different size water fleas

Time and energy required to capture the different size of water fleas

How often prey are encountered under different densities of water fleas

E 6.4The independent variable = different densities of prey with different

ratios of daphnia

The dependent variable was the selection of prey during the three different trials

The prey are set up at three different densities.

The prediction made included: High density only large daphnia will be eaten Low density the feeding will be equally distributed across the sizes of prey.

 Results:

At a high density the large daphnia are the prey of choice but there is still some medium and small prey selected.

At low density the prediction met with a little variation between prey sizes selected Note that when the food supply changed then the Bluegill Sun fish had a foraging strategy which allows it to respond and change it s behaviour in the short term.

There is a high fitness value to be associated with such behaviour.

6.4

E 6.5In some species, males have evolved conspicuous or exagerated traits that advertise

their reproductive worth.

The male bird is a Peacock well known for its magnificent display of feathers.

2. The feathers have been demonstrated to be associated with courtship and mate selection.

3. The male displays and on the basis of a ‘good’ display he will be chosen by the rather dull female bird for reproduction.

In runaway evolution one female develops a whim for a particular male trait that she then passes on to future generations of females. These females start choosing males with the desired trait, which causes that trait to become exaggerated in males over time.

4. The feather display might be regarded as a rather exaggerated trait, where such traits are believed to have evolved by sexual selection

Natural selection is responsible for the selection of purely utilitarian features such as beaks for feeding, testis for producing sperm or eyes for sight. Sexual selection is responsible for the selection of features purely associated with acquiring a reproductive opportunity

E 6.6

Examples of rhythmic behaviour might include those such as:

Diurnal (daily cycles)

Seasonal Cycles

Lunar Cycles

E 6.7Example 1: Krill 

Krill are shrimp-like marine invertebrates. They are important sources of food for certain whales, sharks, seals and penguins.

Krill typically follow a diurnal vertical migration. They spend the day at greater depths and rise during the night towards the surface. The deeper they go, the darker the water becomes, and this makes it more difficult for predators to eat them.

The diurnal migrations of krill depend on accurate monitoring of daylight, which is achieved by their circadian system.

Example 2: Insect-eating bats

The circadian "clock" in mammals is located in a part of the hypothalamus called the SCN. The SCN receives information about daylight from special photoreceptors in the retina.

The SCN sends a message to the pineal gland, a tiny structure in the brain, which secretes the hormone melatonin. Melatonin causes mammals to feel sleepy. In humans, secretion of melatonin peaks at night.

In bats, melatonin peaks in the daytime, which is why they are more active at night? Being active at night is a benefit to bats because they feed on moths, which mainly fly at night. Thus the circadian rhythm of bats helps them to hunt and feed when their prey is most abundant