9.2 Establishing Phylogenetic Relationships Flashcards
What does phylogeny establish?
Phylogeny establishes evolutionary relationships among species and groups of species.
How can cladograms be produced?
Cladograms can be produced by examining shared derived characters.
Where does evidence of hominid evolution come from?
Evidence of hominid evolution comes from the fossil record.
Phylogeny definition
the evolutionary development and history of a species or group
Phylogenetic tree
branching diagram that represents evolutionary relationships among species or groups
Clade definition
an evolutionary branch in a phylogenetic tree
Cladistics definition
a method of determining the sequence of branches in a phylogenetic tree
Cladogram definition
a phylogenetic diagram that specifies the derived characters of clades
Derived characteristics
homologous structures that are common to all the organisms in a clade (e.g. amniotic egg)
What is one of the best clues to assess how closely related organisms are?
Homologous structures are one of the best clues to assess how closely related organisms are
(e.g. human and chimpanzee skulls)
What can hide homologous structures?
Adaptations can hide homologous structures
(e.g. wing of a bat and flipper of a whale)
What can produce analogous structures that can be mistaken for homologous structures?
convergent evolution
How can the relatedness of species be measured?
Relatedness of species can be measured by comparing their genes and the proteins that genes code for
The more similar the _____ are, the more closely the species are related
The more similar the genes the more closely the species are related
-e.g. fossil data indicates whales are closely
related to hippos, cows, deer, and pigs.
-Molecular data now also supports this.
Phylogeny & HIV Evolution
Case Study: Libyan bioterrorism case
-HIV mutates at a fast rate (it’s a virus)
-HIV can evolve into 5 new strains per year
-All infected children were infected by the same
strain
-2 possible scenarios:
-HIV developed from a single strain AFTER 1998
- Medics could have infected the children
-HIV not similar enough to have a common
ancestor after 1998 (this the lineages split
BEFORE 1998)
- Medics could NOT have caused the
infection
conclusions on Libyan case
-Looking at the rate of mutation, scenario 2 was proven
-The strains had been diverging before the medics arrived at the hospital
-HIV was blamed on tainted needles and poor hygiene practices by the hospital, not the medics
Which group were one of the first placental mammals to evolve about 65 mya?
primates
What also occurred 65 million years ago?
dinosaur extinction
Prosimians
group of primates that include lemurs, lorises, tarsiers
Anthropoids
group of primates that include new-world monkeys, old-world monkeys, hominoids
Hominoids
the great apes: gibbons, orangutans, gorillas, chimpanzees and humans*
characteristics of primates
-Grasping hands and feet
-Opposable first digits (thumbs)
-Forward facing eyes or binocular vision (provide depth perception)
-prosimians – lemurs, lorises, tarsiers
-anthropoids – new-world monkeys, old-world monkeys, hominoids
characteristics of hominoids
-Large brains
-Lack tails
-Swinging arms
-gibbons, orangutans, gorillas, chimps, and humans
Hominids
Humans and all their ancestral species that arose after the split from ancestral chimpanzees
Hominoids vs. Hominids
hominoids- primate group that includes gibbons, orangutans, gorillas, chimps, and humans
hominids- humans
Early primates gave rise to two distinct lines:
Prosimians
Anthropoids
Anthropoids branch into:
old world monkeys
new world monkeys
hominoids
Emergence of Hominids
-Large brain size
-Bipedalism (ability to walk on two feet)
-greater efficiency, freeing of hands, vision over
tall grass
-E.g. Ardipithicus ramidus (one of the oldest known bipedal species) dates back 4.6 mya
Bipedalism
ability to walk on two feet
oldest ancestor discovered so far
Sahelanthropus tchadensis 7mya (disc. 2001)
Australopithecus afarensis*
-Early biped
-Lived 3.5 mya
-1m tall, ape-like features
-Lucy most famous representative of species
Which species is Lucy a famous representative of?
Australopithecus Afarensis
Homo Habilis
-First of Homo genus
-2.2 - 1.6 mya
-Larger brain, smaller jaws and teeth, longer legs than A. afarensis
-Brain size approx. half of modern human’s
-First ancestor to use stone tools
Homo Erectus
-1.9 - 1.4 mya
-Body proportions similar to modern humans
-Used stone tools and fire
-Spread into Europe and Asia
-H. ergaster: subspecies of H. erectus
-Evolved into H. heidelbergensis, H. neanderthalensis and H. sapiens
Homo Neanderthalensis*
-350 000 - 30 000 ya
-Stocky species, pronounced brow ridges
-Larger brains
-Fashioned tools, practiced inhumation, complex speech
-We have neanderthal DNA in our genome which proves we interbred
Homo Sapiens
-Modern humans
-First appear in Africa 130 000 ya
-Large brains, complex speech, inventive and
ingenious
-Dexterous
-Long childhood dependency
-Produced art
Out of Africa Theory
-Oldest H. sapiens fossil found in Ethiopia
-Indicates modern day humans evolved in Africa
-DNA evidence supports this
-First wave of migration to Asia and second wave to
Europe, Southeast Asia, and Australia
-North America ??
-Founder Effect visible in human populations outside Africa
True or False: Early human fossils have been found on different continents; however, all modern
humans have a ____________
common African ancestor
Explain how cladograms are constructed
The key rule in cladistics is that all of the organisms of a particular clade must share homologous structures that do not occur outside the clade.
These homologous structures that are common to all the organisms in a clade are called derived characters.
(A phylogenetic diagram that specifies the derived characters of clades is called a cladogram)
What are two subdivisions within the primate
family?
prosimians and anthropoids
What features are common to all hominoids?
Hominoids have relatively large brains, lack tails, and have swinging arms
What organisms are included in the hominid
family?
Hominids are humans and all their ancestral species that arose after the split from ancestral
chimpanzees
What distinguishes hominids from all other species?
their large brain size and bipedalism (ability to walk on two feet)
How is the Homo genus different from australopithecines?
The first members of the genus Homo are believed to have co-existed with some species of australopithecines. Members of the Homo genus differ from australopithecines by their larger brain size and the shape of their jaws and teeth
How has phylogeny been used to solve a crime?
-scientists traced the phylogeny of HIV and found HIV mutates at a fast pace, so new strains of the virus arise quickly.
-In fact, HIV can evolve into five new strains a year.
-Scientists examined the HIV viruses in the infected children and found that the viruses were very
closely related to one another
-therefore, it was likely that all children were
infected from the same source
-The scientists then looked at the rate of mutation in the viruses to determine when the different strains developed.
-Their analysis revealed that in fact the second scenario was correct.
-The strains had been diverging before the medics arrived at the hospital.
-The scientists blamed tainted needles and poor hygiene practices by the hospital, not the medics, for infecting the children
Some argue that birds belong in a separate
clade from crocodiles. Why do you think
they believe this?
according to Linaean classification(morphology), organisms are grouped by characteristics regardless of their ancestry. So a reptile is an animal that is ectothermic and has scales, and birds would not be reptiles
Which trait most likely evolved first, backbone, legs or hair? Explain
backbone because it helped vertebrates conquer the oceans and move onto land, and survive and adapt to their environments
(a) Which do you think evolved first in human
ancestors: bipedalism or large brain size?
(b) What evidence is there that supports your
answer to (a)?
bipedalism
-Hominins started walking bipedally long before the brain expanded,
What does the discovery of Ardipethecus
Ramidus tell us about human evolution?
This shows that both humans and chimpanzees have evolved different features, and both
species now look very different from their ancestors
shows that humans did not evolve from a “chimpanzee-like ape.”
-they meant that Ardi evolved from an ancient ape that didn’t look like a chimpanzee or gorilla does today and that humans have retained some of those primitive trait
Homo neanderthalis and Homo sapiens lived
at the same time but did not interbreed. If
you were to find neanderthal DNA and
compare it to modern human DNA, what
would you expect to find if the above
hypothesis were correct?
DNA that’s different from each other
All modern humans are believed to have arisen
from a common ancestor that lived in Africa.
What evidence did scientists use to determine
whether this is true?
The oldest H. sapiens fossils have been found in Ethiopia, which indicates that humans evolved in Africa.
-Recent DNA evidence supports this.
-Humans then migrated to other parts of the world
Examine the hominoid skull. What would you have to do to decide how it fits into the human phylogenetic tree?
-check to see if it has a large brain size, jaw, structure
-see if they share similar characteristics to chimpanzees (humans are more closely related to them)
-if they do they would be placed within the
humans clade
-if they share characteristics with gibbons or orangutans, then they would be placed within that clade
What is the key rule in cladistics?
all of the organisms of a particular clade must share homologous structures that do not occur outside the clade
derived characters definition
homologous structures that are common to all the organisms in a clade
Why are analogous structures not useful for classifying species in an evolutionary context?
convergent evolution can produce analogous structures that can be mistaken for homologous structures
which group of primates do hominoids belong to?
anthropoids
true or false: anthropoids have binocular and colour vision
true
which species is more similar to early
humans and ancestral apes than it is to chimpanzees?
A. ramidus
which species practiced inhumation?
homo neanderthalensis
what is inhumation
burying the dead
which species used fire
homo erectus
which species used stone tools
homo habilis
which species had pronounced brow ridges
homo neanderthalensis
which species produced art?
homo sapiens
the migration pattern of early Homo sapiens around the world was obtained through…
DNA evidence
