Chapter 6: Adaptations Flashcards
What do adaptations mean?
They simply mean that some individuals in a population can survive and reproduce more than other individuals. If a trait helps an organism survive and reproduce in its environment, then it is an adaptation.
What is an easy way to remember what adaptations do?
Adaptations = advantage
What is an analogy you can use to remember how natural selection creates adaptations?
Think of the selective pressure as a biased dad and the different traits as the children. Say both the children made a mistake and the dad needs to punish them. Because the dad prefers the first kid because of his blue eyes, he is going to let him off easy and let him live. But for the other kid that has brown eyes, the dad is going to off on him. So the dad let favouritism affect his decision of who he was going to punish and who was going to survive. So having blue eyes will be an adaptation in this toxic home environment. Just like in an environment, if the selective pressure favours one trait over the others, that trait will be abundant in the population because it helps individuals who have it to survive and reproduce.
What are three ways to test the adaptive hypothesis?
- Direct study of natural selection: provides evidence associated with the fact that populations adapted to a specific type of environmental pressure.
- Comparative approach: This involves comparing adaptations among groups and determining which traits evolved independently ( convergence) or which are the result of a common ancestor. For example, comparing how the eye of the octopus differs from the eye of a vertebrate. This type of method allows us to pinpoint where the adaptation originated from. This helps us to ask the question of why did the common ancestor evolve that trait? For example, looking at the evolution of the cheetah, we see that their ability to walk on their digits is not unique to cheetahs but is rather found in all carnivores. Then we can ask ourselves why did the common ancestor of carnivores evolve this digitigrade type of walking?
- Morphofunctional study of a trait: when you look at an adaptation now and its function now, it may not reflect why the structure evolved in the first place
Explain why choking is possible in humans but not primates?
In chimpanzees, when they eat, the food pass through the mouth (duh) and pushes against the soft palate and its mass weighs on the epiglottis, causing it to flatten out and cover the trachea to keep food from entering it. This is automatic. With this, the food is able to move into the esophagegus. But in humans, there is a space between the soft palate and the epiglottis and this is what causes chocking. Chocking occurs when food enters the trachea and gets stuck there. with the way the human mouth, tongue, and jaw are (they are small as we do not spend a lot of time chewing), there is a probability that the food may end up in the trachea because there is not an automatic shut down of the epiglottis when you swallow food. It may be that as food enters that space, the epiglottis remains open and the possibility of chocking is there
How is the act of chocking a result of evolutionary compromise?
In humans, there is a space that goes from the soft palate to the vocal cord. In this space, there are a lot of nerves and muscles. So it is a very complex intricate system of contractions that will actually create vowels and consonants that we use in language. So this space actually gives us the ability to speak and to have articulated speech. And it seems that the evolutionary advantage of communicating between humans far outweighs the disadvantage of having the space there that may result in choking. So it seems like this is an evolutionary compromise between two selective forces: the ability to communicate and the danger of choking on your food.
How does the epiglottis prevent chocking? In essence, what does it do?
The epiglottis will shut the trachea and will prevent things such as food from entering the trachea, and will therefore protect the respiratory tract. Chocking is a result of food entering the trachea
What are the three kinds of symbiotic relationships? name and explain each
The first kind is mutualism. In this kind of relationship between two organisms, both organisms benefit from each other.
The second kind is commensalism. In this kind of relationship, one of the two organisms is benefiting from the relationship while the other is not.
The third kind is parasitism. In this relationship, one of the two organisms benefits from the relationship while the other is being harmed. An example of this is the flatworm which lives in the stomach of human beings. These parasites can actually be found on the skin of salmon in sushi. While living in your stomach, they eat what you eat and start feeding on necessary vitamins. While they are benefitting, the human is getting sick.
Given an example of when scientists believed a symbiotic relationship was commensalism when it was actually mutualism?
Burying beetles carry mites on them. They feed by burying a dead cadaver so that other insects do not have access to them and so that they can lay their eggs not far from the cadaver. What they will do is that they will alternate in that they will chew on the cadaver and feet it to their young at the same time and the eggs will hatch and grow in the cadaver until they are adults and go look for their own cadaver. The mites use the beetles as transport so that they can access cadavers because they also have their life cycles in the cadavers. At first, scientists believed this relationship was commensalism because it seemed like the mites were using the beetles as transportation to cadavers and that the beetles were not getting anything in return. Turns out the symbiotic relationship between the two is actually mutualism because the mites kill and feed on any competitor of the beetles, giving the larvae of the beetles the ability to survive and feed properly in the cadavers.
What is an interesting pattern noticed in T-rex dinosaurs?
The smallest species tend to be the oldest species.
Why is it important to look at the history of a species to understand where the adaptations came from?
- Trying to understand why certain traits are in organisms and only looking at the current organisms to explain why does not make sense, we need to look at the history of the organism to see why this adaptation is present in the current species.
What is an exaptation and how is it different from an adaptation? Also give an example of this.
An exaptation is a structure that has a different function from the original function for which the structure was evolved. Adaptations are different in that their current function is the reason for why they were evolved, while the function that exaptations have now will be different from the function they had originally. A good example of an exaptation is in elephants. Elephants live in Africa where there is a lot of heat from the sun. For this reason, they need to be able to lose heat. An unusual thing about them is that they thin coarse hair on their body. The trait of hair helps animals preserve heat, and the question that arises is why do elephants have this trait then? They want to be able to lose heat not preserve it! We cannot say that the elephant evolved hair through convergence because it would not make sense as to why other animals have it. So the only explanation behind this is that this trait is an exaptation in elephants. It has a different function, helping these organisms lose heat, compared to its original function for which it was evolved, preserving heat.
What is heterochrony and what is it responsible for?
This deals with changes in the speed or synchronization of the developmental phases. It is responsible for the modification in how the chimpanzee and human heads grow
What is paedomorphosis and provide an example of how it occurs
There is a species of salamander called axolotl and through paedomorphosis, it develops its sexual organs faster than its somatic organs so its full body. They develop their reproductive organs at the tadpole phase. So they become sexually mature and do their reproductive cycle as tadpole in the water and therefore never have a terrestrial phase, even though they still have larvae characteristics like gills. It is the change in the development speed of the reproductive organs that provoked this. For this reason, they never have a terrestrial phase where they live on land and are seen
