Animal Skulls CHaOS+

Introduction
Public summary: 

What type of bone are SKULLS? What are their features and how are they linked to their FUNCTION? You can find out how different animals evolved to suit their habits and their habitats and some fascinating comparisons between species!

Looking at different animal skulls to compare them and see how they differ.
Useful information
Kit List: 

Various different skulls and a pile of laminated photos

Box 1
Mammals: sheep, dog, cat, fox, mole, rabbit, roe deer
Birds: magpie, pigeon, oystercatcher, duck (one complete, one in parts), parrots
Other: gulper shark jaw, striped snakehead fish, snake (some kind of boa)

Box 2
Primates: human, chimp, gorilla, orangutan (all models)

For CBS, some can also be borrowed from the zoology museum.

Pictures of the animals

Packing Away: 

Please pack each skull carefully into each individual box, which will be labelled with the animal names and packing instructions. Inside the lid of the main boxes there's a diagram of how to fit the smaller boxes inside.

Frequency of use: 
5
Explanation
Explanation: 

***OVERVIEW***

We have some skulls of different animals. Each has different adaptations relating to the animal’s lifestyle and environment. Looking at a skull’s characteristics, such as teeth, eye placement and size, scientists can determine whether the animal was an herbivore, carnivore, or omnivore, and if the animal was a predator or prey animal.
There are lots of anatomical features of the skull that make it suited to its function.

***SETTING OUT THE EXPERIMENT***
In a calm event it can be nice to set out all the skulls on a table, with all the photo cards spread out in front of them so that you can play a matching game. In a busier event or with an excited group of kids it's probably better to have them in the big blue boxes and pull out one skull at a time, or choose a few skulls you like that fit a narrative (e.g. comparing herbivores and carnivores) and have just those out. That makes it easier to control which kids are holding the skull(s) and it makes it easier to control the questions, as you don't have to jump backwards and forwards between lots of different animals!

***BASIC PROCEDURE AND EXPLANATION***

Animal skulls experiment is flexible and you can talk about the skulls that you find cool or know more about.

You could start talking about one skull in detail and how it is suited to its function. Then you could move on to comparisons with other skulls to the first one you picked. It's easier to pick one of the bigger/ less fragile skulls first, such as the human (made of plastic!) or the sheep skull. Make sure that you've established what a skull is on the first one- it's not as obvious as you might think that it's the boney stuff that is inside our head/ protects our brain. You might also want to briefly talk about what bones are for/ made of - an explanation of hard stuff that holds our bodies up is probably enough detail for the youngest kids!

* Start by selecting a skull of a species that you are going to focus on.
* Discuss what the skull is made of- bone. The skull is made up of flat bones.
Bone is made of 1/3 organic type 1 collagen and 2/3 hydroxyapatite with adsorbed calcium carbonate. Skull bone is formed from condensed sheets of fibrous tissue- cancellous bone and marrow sandwiched between two layers of compact bone and periosteum - this is called a diploë
(Compare this to long bones which are different. Long bones are made up of osteoblasts and osteoclasts. Osteoblasts are uninucleate cells that live as long as the animal and are responsible for formation of the bone matrix. Osteoclasts are myeloid derived blood cells which are multinucleate, short lived and are in control of bone destruction. Together these types of cells are in charge of bone formation and destruction. This is a feature of bone in general and applies to the skull as well under the control of parathyroid hormone, calcitonin and vitamin D. Another example of a flat bone is the scapula)
* Discuss how the skull bone is formed developmentally- it is formed from pharyngeal arches. The toothed, upper and lower jaws are dermocranium- they form around viscerocranial cartilage templates from pharyngeal arches.
* The skull is made up of lots of different bones: premaxilla, maxilla, vomer, nasal, palatine, lacrimal, frontal, parietal, interparietal and tympanic bones. There are also also teeth.
* On the skull you have taken- can ask if they know the names of any parts of the skull. Key features to notice:
- The cranium contains a cavity that has the main function of containing the brain.
- Eye sockets- supports the eye balls. There is a nasolacrimal fossa for the sac and the duct. There is a hole at the back of the socket through which the optic nerve runs
- Tympanic bullae are the bulges associated with the auditory canal- these have the function of amplifying sounds and particularly low frequencies.
- Nasal conchae are scrolls within the nasal canal and these increase surface area for the olfactory epithelium to cover which
- The foramen magnum is the main cavity at the back of the skull and this is where the spine attaches to the skull. The spinal cord runs through this hole and connects to the hindbrain.
- The mandible is used for creating a hinge join at the temporomandibular joint which allows jaw movement
- The mandibular symphysis is the joint in the chin where the two bones of either side of the mandible are fused– note that this is one of the most common ‘fractures’ to result from cat/car impacts. The symphysis fuses in horse around two years of age and may also fuse into a ‘synostosis’ late in life in ruminants.
- Other holes in the skull are for nerves. The cranial nerves are:
I- Olfactory nerve
II- Optic nerve
III- Oculomotor nerve
IV- Trochlear nerve
V- Trigeminal nerve
VI- Abducens nerve
VII- Facial nerve
VIII- Vestibulocochlear nerve
IX- Glossopharyngeal nerve
X- Vagus nerve
XI- Accessory nerve
XII- Hypoglossal nerve
These allow the brain to connect to send and receive signals from the rest of the body.
* Can then move onto the other skulls - discuss the features of the skulls and how these relate to the demands that the animal has to cope with in its environment. Why might the adaptations help the animal to succeed in its environment/why might the animal have developed these skull features? You might want to discuss each skull in turn, or you may prefer to talk about a particular 'theme' i.e. teeth, brain size across a number of skulls at once
* Allow the students to handle skulls so they can feel how delicate/sturdy they are
* Note that delicate skulls have a small piece of red gaffa on their boxes - only let children handle these if you think they will be careful enough with them!

Interesting features/comparisons include:

TEETH
- The type, shape and number of teeth an animal has can help determine its diet.
- Incisors are the front teeth. They are used primarily for cutting and grasping.
- Canines are the teeth next to the incisors. The canine teeth typically are large in a predator and are used for tearing and grasping.
- Premolars are the teeth behind the canines. These teeth have sharp edges for crushing food.
- Molars are the very back teeth. They are broad and flat and are used for grinding.

If a mammal has long, sharp canines, it is most likely a predator. Canines are used for grabbing, holding and killing prey. Some meat-eating mammals (carnivores) have sharp shearing cheek-teeth called carnassials. These teeth act like a scissor to cut through tough flesh and to break it into smaller pieces for swallowing and digestion. The fox is mainly carnivorous, although they also gather a wide variety of other foods like fruit and berries. The European Mole is also carnivorous, and feeds on invertebrates e.g. earthworms, insects. Ask the child if they can think of any other carnivores (cats and dogs are just two familiar carnivores).

Plant eating animals tend to have teeth specialized in chewing various parts of plants. Some plant eaters eat grasses (grazers e.g. sheep, using incisors to nip plants close to their bases), some eat twigs, leaves and berries (browsers e.g. goats/deer) while others eat only specific plant parts (i.e. roots, fruit, etc.). In order to properly digest vegetation, an animal must chew its food to help break down the plant. Most herbivores have cheek teeth called molars. These molars help grind leaves, stems, grasses, fruit and even seeds before the animal swallows them. Examples of herbivores in our skull collection include the hare (hares eat grasses during the summer and twigs/tree bark etc. during the winter, and also commonly re-ingest their faecal pellets...) and the sheep (these mainly feed on grasses, have a large and complex stomach which is able to digest highly fibrous foods that cannot be digested by many other animals). Sheep, cows, llamas and alpacas all don't have top inscisors! Instead they have a thick, hardened gum line called the dental pad which they use to pinch off blades of grass against.

Some animals (omnivores) eat both plants and animals, and have both types of teeth. The primates and magpie are omnivores (although obviously the mapgpie doesn’t have any teeth). Interestingly though, recent studies have shown that chickens (and possibly other bird species) still retain the genetic blueprints to produce teeth in the jaws, although these are dormant in living animals. These are a feature from primitive birds such as Archaeopteryx, which were descended from theropod dinosaurs. Other examples of omnivores include pigs and bears.

Fish - some fish have teeth, others don't. They tend to all be small and sharp if they have them and are mostly found in carnivorous species. This fish eats frogs, insects, and smaller fish. It has small and large teeth but they are all the same shape.

Snake - snakes have long sharp teeth. Venomous species have venom teeth which have either a groove or a hole running through the tooth, through which the venom is injected. These are the only specialised teeth in snakes.

Shark - sharks have many sharp teeth. Their teeth often fall out as they grab moving prey and so they have a continuous 'conveyor belt' of teeth growing from their jaw. The new teeth that aren't needed yet lay flat against the jaw until the tooth in front falls out and they they move up into the normal tooth position. You can see the new teeth ready to move up on the inside of the jaw.

BEAKS
You might want to talk about how birds such as the chicken use their beaks to feed, and talk about how other birds have adapted their beaks to help them eat their chosen food.

The beak of a bird is an extension of its skull and is designed for feeding. Some beaks have evolved to specialize for feeding on specific items.

Duck: wide flattened "bill" used for eating aquatic plants and mosses - specialised for "dredging" type jobs. Dabbling ducks, which feed on the surface of the water (or as deep as they can reach by upending without completely submerging) have a comb like structure along the edge of their beak called a pectin - this strains the water squirting from the side of the beak and traps any food. This can be seen on one of our duck skulls. Also used to preen feathers.

Parrots: seeds are the most important part of their diet, which has led to the evolution of a large and powerful bill which is primarily an adaptation to opening and consuming seeds.

Oystercatcher: bill shape varies between species, according to diet - birds with blade like bill tips pry open or smash mollusc shells, and those with pointed bill tips tend to probe for annelid worms.

Pigeons: homing pigeons have iron containing structures in their beaks which may enable the birds to use the earth's magnetic field for navigation

Other birds (which we don't have, but that you could discuss) include - the hawk, which has a sharp hooked beak used in tearing flesh from its prey or carrion. A hummingbird uses its long narrow beak to lap nectar from flowers and a sparrow has a small powerful beak used for picking berries and cracking seeds.

NOSES
Noses are not part of the skeleton. They are made of either cartilige or muscles and nerves. The nose sizes are linked to the sense of smell. Cats have a better sense of smell than dogs? etc (dogs are 10,000 times more sensitive to odors than humans). Apart from food, what else do animals need noses for? (smelling mould, predators, recognising family members, detecting when another animal is in heat). The sheep skull has large nasal cavities, with delicate rolls of (turbinate) bones, which support a large area of nasal epithelium (skin inside the nose) for many, many scent receptors and to reduce heat/moisture loss. Nose length varies in dog species-
Dolicephalic- long nosed breeds like greyhounds
Brachycephalic- short nosed breeds like pugs
Mesocephalic- medium nosed breeds like terriers

EYE PLACEMENT AND SIZE (particularly relevant to mammals)
Large eye sockets suggest an animal is active at night (nocturnal). In this case, a larger eye has evolved to allow the animal to see better at night. Moles and cats (very obvious large eye sockets) are nocturnal, hunting prey and remaining active at night.

Eyes that face forward on a skull suggest a predator (‘an animal that hunts other animals for food’). Forward facing eyes allow for binocular or stereoscopic vision, which allows an animal to see and judge depth. Predators need this depth perception to track and pursue prey.
The fox is an example of a predator in our collection. The orangutan also has forward facing eyes that give it depth perception needed to swing and leap in their tree top habitat. Humans have forward facing eyes as well (you could talk here about us being descended from apes).

Animals with eyes that are located on the side of its head would suggest a prey animal. Side eye placement allows for greater peripheral or side vision. This enables the animal to see predators approaching from the side as well as from behind. This vision is very important for protecting an animal when it is grazing or feeding. The hare is an example of a prey animal in our collection. Other examples include deer and rabbits.

"Eyes in the front, the animal hunts. Eyes on the side, the animal hides."

CRANIUM
The size of an animal’s cranium (relative to its body size) can give you an idea of how well developed its cerebral cortex (the part of the brain that contributes to ‘intelligence’) is. The size of an animal’s cerebral cortex can be used as a rough indicator for how 'intelligent' it is as a larger brain gives more processing power. A good way to compare the size of the brain cavity is to look at how big it is relative to the rest of the animal’s skull. Generally, social animals such as monkeys, apes (including humans), dolphins, and elephants have large cerebral cortices. This is because keeping track of social relations within the group requires a great deal of ‘processing power’.

Magpies are a member of the corvid family - group of birds including crows, jackdaws etc. - these birds are thought to be the most intelligent of all bird species, and have larger cerebral cortices than would be expected for their body size. This intelligence is demonstrated in several ways e.g. European magpies have shown self awareness (i.e. recognising themselves) in mirror tests, crows and rooks have tool making abilities (e.g. hooks to 'fish' for grubs) - things that people generally associate with higher mammals such as ourselves and other apes. These birds also have highly complex social lives, just like apes (need to have large brains with lots of computational power to keep track of what other animals are doing, understand their relationships with other animals in the group etc.).

Parrots also highly intelligent and have high brain size to body ratio - some have been shown to be able to associate words with their meanings and form simple sentences (e.g. Alex the African Grey), some species of parrots are highly skilled at using tools and solving puzzles.

Pigeons, by contrast, seem to be less "intelligent". If a pigeon is taught that doing something (e.g. pecking at light A) leads to reward, and doing something else (e.g. pecking at light B) doesn't, then they can learn these rules, but if you change the rules around (e.g. pecking at A doesn't lead to a reward, and pecking at B does) they find it difficult to "reverse" their behaviour (whereas corvids and humans manage easily!) As pigeons are a similar size to magpies, comparing the size of these 2 skull's craniums is a good example of how cranial size can indicate intelligence. Another good comparison is the human and the chimpanzee.

NB Unlike most other apes, orangutans are shy, solitary animals. They live alone in large territories. This is probably due to their eating habits; they need a large area in order to get enough food and too many orangutans in one area might lead to starvation. However, they are very intelligent. They have been known to use found objects as tools; for example, they use leaves as umbrellas to keep the rain from getting them wet. They also use leaves as cups to help them drink water.

TEMPOROMANDIBULAR JOINT
This is the 'jaw joint between the cranium and the mandible. In carnivores it is quite limited to a dorsoventral hinge movement (in badgers the lower jaw is so firmly hinged that it cannot be detached). In contrast, in herbivores there is much lateral grinding movement as well. The temporomandibular joints each contain a disk similar to the menisci of the stifle, and like the menisci, the disks may help to partition the movements of the jaw joint into compartments (hinge-like between disk and mandible, translation between disk and skull)

*** OTHER THINGS TO TALK ABOUT ***

Distinctively-shaped skulls that some animals have might they have developed to be like that E.g. crocodile, hammerhead shark, elephant (tusks)...

If the child is old enough and seems keen, you might want to touch on the concept of natural selection (survival of the fittest) and how this drives development of the peculiar features that some animals have. For example nocturnal animals will have more success catching food and escaping predators if they have large eyes that let in as much light as possible in low light conditions. Animals with smaller eyes than average will find it more difficult to do this and are less likely to survive than animals with larger than average eyes. The animals with larger eyes will therefore be more likely to survive and have babies, who will in turn also have big eyes like their parents (you will need to briefly touch on genetics here too – has the child noticed that they share the same eye/hair/skin colour/nose shape etc with their parents?)

These are some other comparative anatomy points in domestic breeds:
1) Cat:
Note the domed cranium, huge orbits and short snout.
2) Pig: exhibits dramatic specialisation for rooting
It is extremely tall caudally for the attachment of strong neck muscles. Also, in life there is an extra bone in the snout - the os rostri
3. Ruminants:
Have distinctively domed crania, although this may be obscured by the horns .
The horns are frontal in position in sheep and goats and more temporal in cattle.
Also, the ruminant basi-cranial axis appears rather ‘bent’.
There is no alar canal for the maxillary artery in ruminants. The nasal bones often fall off. 
4. Horse:
Extremely long and the origin of the jaw muscles is extended cranially from the zygomatic arch by the long facial crest .
There is a supraorbital foramen dorsal to the eye through which passes the supraorbital artery (used for arteripuncture) and supraorbital nerve (used for nerve blocks). 
5. Rabbit:
Extremely delicate skulls– sometimes the occiput falls off, which is the bones at the back part of the skull

Risk Assessment
Date risk assesment last checked: 
Tue, 08/01/2019
Risk assesment checked by: 
JenniferSimpson
Date risk assesment double checked: 
Wed, 09/01/2019
Risk assesment double-checked by: 
Grace Exley
Risk Assessment: 

Comparing different real and plastic animal skulls.

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Hazard Risk Likelihood Severity Overall Mitigation Likelihood Severity Overall
Teeth or beaks. Some skulls have sharp teeth or beaks, which can cut/stab children and demonstrators. 3 2 6 Remind children to handle skulls carefully; in particular, be careful not to pinch fingers/hands in the jaw.
Call first aider in event of incident.
2 2 4
Shattered skulls If dropped, skulls may fall on feet or shatter, causing cuts and other injuries. 3 2 6 Demonstrator only have a few skulls present at a time to minimise risk of children picking up or playing with skulls. Demonstrator to keep an eye on anybody holding skulls. If a skull smashes, clear it up immediately with dustpan and brush. Any skulls with sharp edges may need to be smoothed off or replaced.
Call first aider in event of injuries.
2 1 2
Unsanitary skulls Possible infection risk from bone if skin is cut by touching the bone. 2 2 4 We have boiled the skulls we found in bleach for a few hours to sterilise them. Please note, however, this does not necessarily mean that the skulls are completely sterile now. One could give the skulls a gentle clean with disinfecting wipes if they're on hand.
Call first aider to properly dress and sterilise wounds. Warn parents of the possibility of infection if a child does cut him/herself on the skull. Advise parents to take child to a doctor if the cut looks infected.
1 2 2
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Images
Publicity photo: 
Experiment photos: