introduce the idea of Using Dichotomous Keys to help identify things.
We will use this key to do a lab on identifying mammalian skulls. Be careful with these skulls! They are very fragile. We will take two periods to complete this lab.
CLASS NOTES:
STUDY QUESTIONS TODAY:
1. What is meant by the word "Adaptation"?
2. Skull adaptations for predators/prey include the placement of the eyes. Explain why eye socket anatomy is different in predator vs prey. Give examples
3. What teeth do predators have compared to prey?
4. How are the skulls HOMOLOGOUS TRAITS? What is a homologous trait?
5. What is an analogous trait?
IDENTIFICATION LAB:
Purpose:
1. To identify a set of mammalian skulls and determine whether the animal is a predator or prey
2. Demonstrate an ability to use a dichotomous key
3. Draw each specimen and demonstrate your ability to observe using the skill of drawing.
4. Make conclusions about what animal this might be.
For each specimen: 10 marks per specimen:
1. Make a half page drawing where you measure and label parts
5 marks - your color drawing is in ink, and half a page and every part is labeled, and you have measured it in cm
3-4 marks, drawing is not in colour, it is in pencil, or less than half a page or some parts not labeled. or you did not measure, or it is a rushed drawing
1-2 marks - it is incomplete
2. observe the eye sockets and the teeth and conclude whether the skull belongs to a predator or prey
3 marks - you explain yourself very clearly and give your reasons and they seem logical
2 marks - your reasons are logical
1 - you are correct and need to provide more evidence for your point of view
3. Take your best shot at identifying this specimen, give reasons for your conclusion.
2 marks - you are spot on! or, if it is inconclusive, you give your best evidence for what it might be
1 mark- you are making a pretty good guess and you provide some evidence
Some useful information:
Dichotomous Key for Mammals in the USA
Mammals of Alaska
The following quote is from
https://www.earthlife.net/mammals/teeth.html
"Teeth in mammals come in four different sorts: Incisors, Canines, Premolars and Molars. Not all mammals have all, or even any of them and the roles any particular sort of teeth play in an animal's life can be quite diverse. The arrangement of teeth in any given mammals mouth can be expressed as a 'dental formula'. This formula gives the arrangement of one side of an animal's jaw such that incisors are always written first then canines then premolars and then molars.
For humans 2123-2123 is upper and lower jaws respectively signifying 2 incisors, 1 canine, 2 premolars and 3 molars on each side in both the upper and lower jaw.
In total this adds up to 8 incisors, 4 canines, 8 premolars and 12 molars = 32 teeth in humans. Other mammals have different numbers of each sort of teeth in their upper and lower jaws. Hence Smoky Bats (family Furipteridae) have the dental formula 2123-3133 whilst Hyenas have 3141-3131 normally.
Incisors = Cutting teeth - these are the front most teeth in the jaw primarily used for the initial biting of food. They have a straight, sharp cutting edge and one root. In many Rodents they grow continually throughout the animals life, this is because they get warn down gnawing through things.
Canines = Stabbing teeth - normally only 2 pairs (one each side) per jaw. They have a sharp, pointed edge and are used with the incisors to bite into food and or to kill prey. Like incisors they have one root. The tusks of many animals such as elephants are modified canines. They are missing in rodents and most large herbivores (Perissodactyls and Artiodactyls). The gap where the canines would have been is often enlarged and is called a 'diastema'.
Premolars = Next back from the canines. They are generally similar to molars in form and function in both herbivores and omnivores, but in carnivores some of them at least are slimmer and are used to cut flesh. When they (the first lower premolar and last upper premolar) are modified like this they are called the carnassials. Otherwise premolars are teeth we use to crush and grind our food. Their upper surfaces have a broad, lumpy top instead of a sharp biting edge. These small irregular lumps are called cusps. Premolars are called bicuspids in some books, this is because, in most cases, they have two cusps. The prefix bi meaning two. The first upper premolars normally have two roots. The other premolars have one root.
Molars = These are larger than premolars and extremely variable depending on the animal's diet. Like premolars they are used for crushing and grinding food, and like premolars their upper surfaces have ridges called cusps on them. Molars normally have three to five cusps and two or three roots. In humans we call the third molars, those closest to the back of the mouth 'Wisdom Teeth'. If the jaw bone is not large enough to accommodate all the teeth in it, as sometimes happens with humans, these wisdom teeth can become painfully wedged between the back of the jaw bone and the 2nd molars. This condition is known as 'impacted wisdom teeth'."
Example: Domestic Cat
