Download Evolution

Title: Different Types of Evolution
Learning question: What are the different ways that evolution can
occur??
Divergent Evolution
•
A pattern of evolution where differences
between groups of organisms
accumulate to a critical point that leads
to the development of a new species
(speciation)
•
Genetic isolation can account for
speciation
•
Organisms with a recent common
ancestor adapt to suit their new
environment via mutations over
successive generations – divergence
occurs
•
Development of various different species
in this manner is referred to as adaptive
radiation
Adaptive Radiation
• Adaptive radiation is a pattern of divergent evolution –
organisms rapidly diversify to adapt to new
environment and niche
• Tropical forests that covered central Australia gave rise
to very different organisms that exist today.
• Organisms compete to survive changing environment
and divergent evolution led to other Australian
mammals dominating the new environment.µ
Convergent Evolution
• A pattern of evolution when unrelated organisms evolve
similar adaptations in response to their environment e.g.
ant eaters have developed similar structures
• No recent common ancestor and belong to different orders
• Traits and behaviors have developed independently and
coincidentally
• Analogous structures result from convergent evolution –
adaptations of different types of structures that solve a
problem in a similar way
Evidence for evolution: comparative
anatomy
• Examination of physical characteristics of
species, studying:
• Embryonic
• Adult stages of evolution
Modern Life: Evidence for Evolutionary Change
• Developmental biologists
– study the stages of growth
and development from
fertilized egg until mature
adult and beyond.
– When embryos of
organisms are similar, it
shows that they are related
because they have
developed in similar ways.
Embryology
• Embryology is a branch of
developmental biology that
focuses on the early development
of organisms before they are born
or hatched.
• These developing organisms are
known as embryos.
• Embryology is particularly useful
in studying organisms that can be
grouped together as having a
common ancestor and therefore
finds out more about their
evolutionary past.
Homologous structures
•
Homologous structures are structures derived from a common ancestor or same
evolutionary or developmental origin.
•
Homologous structures may not necessarily perform the same function but they
share a common ancestral origin.
•
For example, the forelimbs of humans and bats are homologous structures.
Although they are used differently, the basic skeletal structure is the same and
they are derived from the same embryonic origin.
•
Their similarity in this regard could indicate a likely evolution from a common
ancestor.
Vestigial Homologous Structures
• Vestigial structures
– useless structures that no longer have
a function in one organism but may
still function in a related organism.
– Examples-snake legs, whale pelvis,
eyes in blind salamanders, human tail
bone, etc.
• A pattern of similar characteristics for
both homologous and vestigial structures,
suggests how organisms are related.
Click on the image of the flightless Cormorant to find
out more about its vestigial structures.
Analogous structures
• Features of organisms that have the same function, but not
the same basic structure are described as analogous
structures
• E.g. bats, butterflies and birds all have wings, but no
common ancestor. However, they have adapted to a similar
environment
• Evidence that they have evolved from distinct lines of
evolution
Comparative genetics
• Scientists also compare the DNA of organisms
– DNA is found in the nucleus of every cell and contains
all of the genes that give organisms their traits and
proteins.
– The more alike the DNA, the more related.
– For example, Monkeys are 93% similar and Chimpanzee
96% to humans in terms of DNA.
Protein Conservation
• Proteins that are well suited to their function are conserved,
while others may evolve
• Mutations may change functionality of proteins over time,
however, some mutations may substitute one amino acid for
another that is very similar in charge and shape
Genetic Comparison
• A baseline rate of mutations will always occur
within a population – can be measured within
a species as the mutation rate
• Comparison of genetics between two species
can use mutation rates as a “clock” to
estimate when in time these species diverged
from common anscestor
Comparative Genomics
• Bioinformatics digitally stores, retrieves,
organizes and analyses data
• Used to provide evidence for evolution through
rapid analysis of data gathered
• Data can be used to create molecular phylogenic
trees (molecular phylogeny) to illustrate how
genes evolve and are modified to give rise to
different lineages
What does this Phylogenetic tree tell us about CCR5 and HIV?
Humans and other primates have closely related CCR5 sequences. This means that the SIV
viruses that infect non-human primates didn't have to mutate very much to be able to use
human CCR5 as a coreceptor and infect the human immune system.