辅导 BLGY2220 Evolution, Adaptation and Behaviour讲解 Prolog

BLGY2220 Evolution, Adaptation and Behaviour

Group foraging practical

Instructions for the practical

Briefing. You will work in groups. Different groups will act as replicates, or perform. different component experiments. You will carefully document the results from your own group on the sheets provided, and then we will collate them at the end of the session. BRING SOMETHING TO WRITE ON AND WITH TO RECORD DATA (the datasheet provided is for collating the data for your group at the end of each trial). If these practicals are to work (i.e. produce sufficient data for meaningful analysis), we need reliable data from all groups. By the second practical session we will have a complete data set that will be made available to all on Minerva, so that we can analyse it during the second practical session. Note this will form. the basis of the in-course assessment component.

How to organise yourselves

Subdivide into the following groups, based on the lab plans on the corner of each bench, across the whole class we’re aiming for:

2 groups of 13 (8 foragers, 1 predator, 4 observers)

6 groups of 7 (4 foragers, 1 predator, 2 observers)

As these sessions are split into two groups, there will be 4 groups of 13 and 12 groups of 7 in total. (More data from smaller groups from other years will be added to the final data set.)

If we are a few people short, the demonstrators will join in.

How the experiment will work

Each group will run 3 x 5-minute trials. Foragers are going to try to ‘eat as many seeds as possible’, whilst scanning for and avoiding predators. (As there is no eating in the lab, you will be making spots using toothpicks and a food dye/glycerol mix to mimic the act of pecking for seeds.) Predators are going to prowl and intermittently attack (no leaping over the benches, you get a card to show the attack). To avoid being killed by the predator, foragers will dive for cover (again, no leaping, you have to put your hand on a card). Observers log the number of scans foragers make, impose penalties for being slow to react to the predator, and record the total ‘seeds eaten’. You can swap roles between trials if you like. Have a short practice run before you start collecting the real data.

Detailed instructions:

FORAGERS

Make as many spots on the paper plates as you can WITHOUT USING YOUR HANDS.  Holding the toothpick in your mouth, dip it into the food/dye glycerol mix and then touch the tip to the paper plate to make a small spot. These should be separate actions, one dot per dip. Keep count as you go along, you will need to know your total at each strike as well as at the end of the 5 minutes. You need to be scanning for predators, and the observers need to be able to see when you do this. When you scan, lift your head and obviously look around you. If you spot a predator, stop ‘eating’ and touch the card in front of you quickly, keeping your hand out until told to resume by the predator. If you spot another forager reaching for a card, assume there is a predator and do the same. If predator shouts STOP before you spot them, then just stop and wait until told to resume. If there is a false alarm, the predator will inform. you of this and tell you when to start again. If at any time you have more penalties than seeds eaten/spots made, the observer will tell you that you are dead and you must sit out the rest of the trial.

PREDATORS

You need a stop watch. Walk up and down the opposite side of the bench to the foragers, changing direction randomly and frequently. Attack the foragers (by raising the card above your head) at the 10 specified (and randomly generated) times that you are given, within each 5-minute trial period. Three seconds after raising your card shout STOP and stop the clock (but don’t reset it), so that observers can log data, and impose penalties. As soon as this is done, tell foragers to start ‘feeding’ again - and start the clock again. Stop the trail after 5 min.

OBSERVERS

Each observer watches 2 foragers and keeps a running total of the number of ‘seeds’ they have ‘eaten’ in the game. Whilst watching you should count and record the number of times each forager scans for a predator. When the predator strikes, each forager should tell you how many ‘seeds’ they have ‘eaten’.  Add this to the running total for each forager.  Make a note of the new total and then (working with your other observers) impose the following seed penalties:

· If any forager spotted the predator within the three seconds that the black card was held up and all of the foragers touched their yellow cards, then the last to touch their card gets a 16 point penalty. No other foragers get a penalty.

· If no-one spots the predator within the three seconds that the black card was held up, (no foragers touched their yellow cards) then divide the 16 point penalty equally amongst the foragers (i.e. in groups of 4 foragers everyone gets 4 penalty points, in groups of 8, just 2 each).

· If any forager spotted the predator within the 3 s that the black card was held up and some of the foragers touched their yellow cards, then the 16 point penalty should be divided equally amongst the foragers who did NOT touch their yellow card (if this means fractions of a point, round up, i.e. if 3/8 people did not touch their card, give them 6 penalty points each 16/3 = 5.3).

· Record data as you go, after each strike. If at any time a forager has lost more points in penalties than ‘seeds eaten’ (i.e. a negative number of seeds), tell them they are dead - they must sit out the rest of the trial.  Make a note of the time to the nearest minute on the PREDATOR’s stop watch (Minutes alive) for that forager.

Example:

This is a group of 2 foragers. The predator attacked 3 times. On the first and last attack, forager 1 is the last to touch the card so gets all 16 penalties. On the second attack neither touched the card in time so they each get 8 penalties. Forager 1 died at the third attack, forager 2 survived for the full 5 minutes.

Forager number 1

Forager number 2