EVIDENCE FOR EVOLUTION Fossil Biogeographical Anatomical Embryological Biochemical Vestigial features

Fossil Evidence: Fossils are relics or impressions of ancient organisms Most fossils are found in layers (strata) of sedimentary rock The fossil record traces history of life and allows us to study history of particular organisms Through radioactive dating, geologists estimate the age of the earth at about 4.6 billion years

Fossils are at least 10,000 years old and include skeletons, shells, seeds, insects trapped in amber, imprints of organisms, organisms frozen in ice (wooly mammoth),  or trapped in tar pits (saber-toothed tiger) http://www.tarpits.org Transitional forms reveal links between groups (Example: Therapsids were mammal-like reptiles and Pterosaurs were bird like reptiles)

Biogeographical Evidence: Biogeography is the study of the geographic distribution of life forms on earth Physical factors, such as the location of continents, determine where a population can spread Example: Placental mammals arose after Australia separated from the other continents, so only marsupials diversified in Australia KOALA KANGAROO

Anatomical Evidence: Organisms have anatomical similarities when they are closely related because of common descent Homologous structures in different organisms are inherited from a common ancestor. They have similar structures but can differ in function Example : Vertebrate Forelimbs contain the same sets of bones organized in similar ways, despite their dissimilar functions. Ex human, horse, frog, and porpoise.

Analogous structures are inherited from different ancestors but resemble each other because they serve a similar function. Example: Bird wing & bat wing are both for flight but they are structurally different Vestigial Structures are remains of a structure that is no longer functional but show common ancestry Example: Humans have a tailbone but no tail

Embryological Evidence: During development, all vertebrates have a post-anal tail and paired pharyngeal pouches Organisms that show similarities in their embryonic development may have a common ancestry

Biochemical Evidence: Almost all living organisms use the same basic biochemical molecules, e.g., DNA, ATP, enzymes ... Similarities in amino acid sequences, DNA codes, etc. can be explained by descent from a common ancestor Immunological evidence...common reactions to antigens can indicate an evolutionary relationship

VESTIGIAL ORGANS Did you know that.....

Appendix

Appendix No known use in modern humans Often removed when it becomes infected Speculation: once helped to process cellulose in leaf-rich diet Natural selection  smaller appendices (less likely to become inflamed and diseased)

Coccyx

Coccyx (tail bone) Over time we lost the need for a tail (as tree swinging was replaced by hanging out at the local water hole grunting Neanderthal gossip) Coccyx now functions as a support structure for various muscles and support when you sit down and lean back

Darwin’s Point plica semilunaris

Darwin's Point The point (shown in the picture above) is a small thick nodule at the junction of the upper and middle sections of the ear. Likely used to help focus sounds in animals No longer has a function in humans Only 10.4% of the human population still has this visible left-over mark of our past It is possible that a much larger number of people carry the gene that produces it as it does not always cause the ear tubercle to appear

Third Eyelid

Third Eyelid If you watch a cat blink, you will see a white membrane cross its eye – that is called its third eyelid It is quite a rare thing in mammals, but common in birds, reptiles, and fish Humans have a remnant (but non-working) third eyelid It has become quite small in humans, but some populations have more visible portions than others There is only one known species of primate that still has a functioning third eyelid, and that is the Calabar angwantibo which lives in West Africa.

Wisdom Teeth

Wisdom Teeth Early humans ate a lot of plants – and they needed to eat them quickly enough that they could eat a sufficient amount in one day to get all of the nutrients they needed Extra set of molars  more productive Particularly essential as the body lacked the ability to sufficiently digest cellulose As evolution made its selections, our diets changed, our jaws grew appropriately smaller, and our third molars became unnecessary Some human populations have now all but completely stopped growing wisdom teeth, while others have almost 100% likelihood of developing them.

Plantaris Muscle

Plantaris muscle The plantaris muscle is used by animals in gripping and manipulating objects with their feet – something you see with apes who seem to be able to use their feet as well as their hands Humans have this muscle as well, but it is now so underdeveloped that it is often taken out by doctors when they need tissue for reconstruction in other parts of the body The muscle is so unimportant to the human body that 9% of humans are now born without it.

Extra Ear Muscles Auriculares muscles

Auriculares muscles Also known as the extrinsic ear muscles, the auriculares muscles are used by animals to swivel and manipulate their ears (independently of their head) in order to focus their hearing on particular sounds Humans still have the muscles that we would once have used for the very same reason – but our muscles are now so feeble that all they can do is give our ears a little wiggle The use of these muscles in cats is very visible (as they can nearly turn their ears completely backwards) – particularly when they are stalking a bird and need to make the smallest movements possible so as to not frighten its future meal.

Junk DNA L-gulonolactone oxidase

L-gulonolactone oxidase While many of the hangovers from our “devolved” past are visible or physical, this is not true for all. Humans have structures in their genetic make-up that were once used to produces enzymes to process vitamin C (it is called L-gulonolactone oxidase) Most other animals have this functioning DNA but at some point in our history, a mutation disabled the gene – whilst leaving behind its remnants as junk DNA This particular junk DNA indicates a common ancestry with other species on earth, so it is particularly interesting.

Jacobson’s Organ Vomeronasal organ

Jacobson's organ Jacobson’s organ is a fascinating part of animal anatomy and it tells us a lot about our own sexual history The organ is in the nose and it is a special “smell” organ which detects pheromones (the chemical that triggers sexual desire, alarm, or information about food trails) It is this organ that allows some animals to track others for sex and to know of potential dangers Humans are born with the Jacobson’s organ, but in early development its abilities dwindle to a point that it is useless Once upon a time, humans would have used this organ to locate mates when communication was not possible. Single’s evenings, chat rooms, and bars have now taken its place in the process of human mate-seeking.

Goose Bumps Cutis Anserina

Goose Bumps Humans get goose bumps when they are cold, frightened, angry, or in awe Many other creatures get goose bumps for the same reason, for example this is why a cat or dog’s hair stands on end and the cause behind a porcupine’s quills raising In cold situations, the rising hair traps air between the hairs and skin, creating insulation and warmth In response to fear, goose bumps make an animal appear larger – hopefully scaring away the enemy Humans no longer benefit from goose bumps and they are simply left over from our past when we were not clothed and needed to scare our own natural enemies. Natural selection removed the thick hair but left behind the mechanism for controlling

Video on Evidence & HOMEWORK Read text p. 332-339 Do p. 340 #2, 4-7, 9-12, 16 Be sure to check out the fossils being passed around