adaptations reading questions PDF

Preview

Summary

adaptations...

Description

Reading guide and self-assessment questions, Lecture 5 (Adaptation) Core Concepts from the Lecture and Essential Reading - only the lecture notes are essential reading for this lecture, because Lecture 6’s reading is substantial. 1. Kea parrots in New Zealand use their sharp beaks to eat fat from under the skin of living sheep. Yet the sharp beak is not an adaptation to sheep predation. How do we know this? 1. A sharp beak is not needed for predation. 2. Kea gain no survival or reproductive advantage from the extra food source. 3. Kea had sharp beaks before there were any sheep in New Zealand. Their beaks evolved for a different purpose such as cracking hard seeds, and could be called a pre-adaptation. 4. Sheep have evolved no counter-adaptations to kea predation. 5. We have analysed kea beak genes and see no signatures of recent selection. 2. Looking at the map on slide 12, which of the following adaptations to the local environment has - to our current knowledge - evolved only once in the human population? 1. Adaptation to cold climate 2. Adaptation to the low oxygen conditions experienced at high altitude 3. Arsenic resistance. This has evolved once in South America. Lactose tolerance evolved twice, in two separate populations with domesticated cattle, and malaria resistance four times in different malarial areas. Altitude tolerance has evolved independently in three mountainous areas, and cold tolerance twice, in Greenland and Siberia. 4. Lactose tolerance 5. Malaria resistance 3. Which two of these would be examples of “extended phenotypes”? Look up any terms with which you’re unfamiliar. 1. An acorn 2. An oak apple - this is a gall, an abnormal growth of the oak tree tissues caused by a wasp larva. Although made of oak cells, the gall is an extended phenotype of the wasp. 3. An oak leaf 4. A whole oak tree 5. The shade cast by an oak tree. This is a phenotype that is not part of the tree itself - could it be an adaptation to prevent rival plants from growing, or is it just a sideeffect of efficient use of sunlight? 4. Which of these statements is true? 1. Active camouflage is an adaptation, but passive camouflage isn’t 2. Passive camouflage is an adaptation, but active camouflage isn’t 3. Changing colour for reasons other than camouflage is not an adaptation 4. Neither active nor passive camouflage are adaptations 5. Both active and passive camouflage can be adaptations. Both improve survival, either by protecting the individual from predators or allowing it to hunt effectively. The use of colour for other purposes such as communication can also be adaptive.

5. Short answer question: Give an example of a well-adapted molecule. What does it do and how does it provide a selective benefit to the organism that produces it? Pretty much any enzyme and most other proteins will work here! The example in the lecture

was topoisomerase II, which disentangles DNA during replication and allows a cell to divide effectively, meaning a unicellular organism can reproduce faster and a multicellular one can grow faster. Deeper Understanding from the Recommended Reading The recommended reading (Trut, L., 1999. Early canid domestication: the farm-fox experiment. American Scientist, 87: 160-169) describes a long-term experiment with an interesting historical background, which raises ethical as well as scientific questions - see the last page in particular. Questions for thought and discussion: 1. What were Morey’s and Belyaev’s competing explanations for the set of characteristics that often accompany domestication? Morey thought that many of the changes were side-effects of selection for small size and early reproduction - this led to paedogenesis, the retention of juvenile traits (such as short snouts and floppy ears) into adult life. Belyaev, on the other hand, thought that paedogenesis and other characteristics of domesticated animals were side-effects of selection for behaviour: specifically tameness, a reduction in aggression and fear. 2. What evidence has the fox experiment produced that helps answer this question, and whose explanation does it favour? The results of the experiment favour Belyaev’s hypothesis. He selected the foxes only for tameness, and found that the other characteristics arose at the same time. The tame foxes are no smaller now than when the experiment began, but still show changes in skull shape to give shorter, more puppylike snouts. However, note the experiment did not include a control! 3. Why did Belyaev chose the fox for his domestication experiment? Belyaev chose foxes because they were related to dogs but had never been domesticated, and because they were already being farmed and so the very first step of removing the animals from the wild and establishing a population that could breed in captivity - referred to as “initial trauma” on page 163 - had already been achieved. 4. If you were planning to start another long-term domestication experiment now, what species would you choose and why? And would you conduct the experiments differently? There are a huge number of possible answers to this question and none of them are really wrong! Some thoughts off the top of my head - you’ll probably have others: · A more distantly related animal would let you see whether the same “rules” apply across a greater evolutionary distance. Perhaps a marsupial, like a quoll? · Belyaev’s experiments selected for a lack of aggression and fear, but didn’t separate the two factors out. It might be possible to do that either by choosing an animal with less aggressive tendencies to begin with, or selecting for fearlessness and non-aggression separately. · Belyaev’s foxes might have been adapting to life in cages as well as to human contact, so it might be valuable to raise the animals in a more natural environment.

Extra Challenge from the Further Reading Choose from among the papers cited and linked in the Notes pages to the lecture slides. These include a 1976 paper describing the experiments and debates surrounding the discovery of the honey bee waggle dance and its function, a more modern paper describing how it discovered that Venus Flytraps can count up to 60, and a review of known examples of local adaptation in humans....