Lecture 2 – The Tree of Life PDF

Lecture 2 – The tree of life Part 1. The importance of the tree of life Medieval view is about 500 to 1500AD. This is La scala naturae. Bottom minerals, then fire, plants, animals, human and the top God and God’s Palace. The higher in the chain, the more attributes it has ...

Lecture 2 – The tree of life Part 1. The importance of the tree of life Medieval view is about 500 to 1500AD. This is La scala naturae. Bottom minerals, then fire, plants, animals, human and the top God and God’s Palace. The higher in the chain, the more attributes it has  Linnaeus’ Kingdom of animals refers to the classification system proposed by Carl Linnaeus in his groundbreaking work systema Nature (1735). At the top of each stack, it has crown organisms. For example, at the bottom of the insects, we have things like fleas and lice. And at the top was cockroach. Kingdom – animalia, Phylum, class, order, family, genus and species. Even now we have medieval thinking. The idea of creation like if humans have evolved from chimpanzees why do they still exist? it is still medieval thinking  Charles Darwin broke medieval approach of medieval He thought that there were fossils he could see that no longer existed. As we could tell, there is the same number of organisms on the Earth and therefore some organisms must disappear and be replaced by other forms. He drew sketch conatinig Groups of living organisms, B, C, and D, were linked in a chain, but many forms between them had died out, making their relationships hard to see. Though correct, he didn’t know the mechanism, as genetics was just emerging, and information spread slowly.  Edwin Hitchcock 1840 came to the same view. He got the animal kingdom on the right and plant kingdom on left. We see branching into life and the extinction of others. This suggests Darwin was alone, but he’s the one who really published his grand opus and made a big splash. And here it is 1859, the only figure from ‘On the Origin of Species’.  We said we got genetics, and we have mutations then clearly evolution should be redefined as a change in the allele frequency in a gene pool. He wrote an article about the teaching evolution in particular in American US schools. Part 2: Lineages changes and diverge over time Making tree of life we use behavioral and ecological, molecular and morphological. The shape of plants, the shape of animals  Using morphological evidence from living whales and fossil whales to track where does whales come from and what their closest living relatives are and how do they change over time. The baleen whales lost upper and lower jaw instead they have stiff skin. They suck in seawater full of shrimp and small particles, then close their mouths and expel the water, trapping the food in their baleen made of keratin. This makes them filter feeders. Predator whales chase down their prey. These are toothed whales.  Some features to do morphology have no value in classification. Mammalian features like placenta, milk production and hair follicle. These features can be used to classify whales as mammals. Features use for classification are homologous traits, derived traits and apomorphias Placenta, milk production and hair are apomorphies for mammals.  Your hands are apomorphic with the fins of a whale. Each stage of the mouse fall in footplate and staining with a dye called alkaline orange, that all living cells stain green. Those that are dying start to stain orange is where we see cell death along the margins. Cell death causes the carving, the formation and the sculpturing of digits. By the time you get the embryonic stage 14.5, the mouse has got separate digits. Similar human fingers grows not because human grows finger outwards but human kills tissues in between the finger and this process is called apoptosis. Whales have massive bonds, more joints than human but there is no apoptosis  It has hidden features of apomorphines, so classification is not straightforward. So, take into account some features have value in classification, and some have greater value. It has legs that are well formed but completely hidden but those legs are apomorphic.  Ancient whales have one sided thicken adaptation for hearing sound in water. One side is thick and other thin It's a thickened involution of that tympanic bulla. Pakistani whale, 50 million years old, 10 million years older than Britain. And look, it's got a tympanic bulla.  Ox has high ankle and there is bone called astragalus. Both deer and pig have astragalus as well. Evolution of Whales: Key Points Whale Types:  o Baleen Whales: Example - Humpback whale o Toothed Whales: Example - Orca Shared Evolutionary Traits: o Both baleen and toothed whales are closely related through the loss of rear limbs. o This shared trait is an example of synapomorphy (a derived characteristic shared by an evolutionary group). Extinct Ancestor: o Doryodon (denoted by 'X' for extinction) shares common features with both baleen and toothed whales. Mammalian Evolution & Molecular Evidence Protein/DNA Comparison: o Milk proteins and cytochrome b (mitochondrial protein) analyzed. o 26 genes and jumping genes studied for evolutionary changes. Key Evolutionary Insights: o Artiodactyls (camels, giraffes, cattle, deer) split from other animals 50+ million years ago. o Whales share a common ancestor with hippopotamuses (land-dwelling whale relatives). Molecular Evidence:  o Combining protein sequences, gene data, and jumping genes clarifies how species evolved and branched. Part 3 – Reading phylogenetic trees: cladistics Each branch, there is a node. From each node, there is two or more branches and at the base we have the ancestral population (the root). You can draw so many trees You read branches from nodes  Terminal taxa can change even though relationships are not changed. Each node and associated branches form a clade. Clade is organism and everything which derived with it.  Actually there is no such thing as fish, says cladist since a clade contains an ancestor and its descendants, then fish captures amphibians, mammals, reptiles and birds as well.