Two species are more related
if they have a more recent common ancestor
, and less related if they have a less recent common ancestor.
Molecular clocks
are used to determine how closely two species are related by calculating the number of differences between the species’ DNA sequences or amino acid sequences. Molecular evidence for evolution includes that all living things share the same biochemical building blocks.
In biology, a
species complex
is a group of closely related organisms that are so similar in appearance that the boundaries between them are often unclear. … As informal taxonomic ranks, species group, species aggregate, macrospecies, and superspecies are also in use.
The DNA of related organisms shows similarity between the species
because some genes will have the same or similar sequences
.
DNA and the genetic code
reflect the shared ancestry of life. DNA comparisons can show how related species are. Biogeography. The global distribution of organisms and the unique features of island species reflect evolution and geological change.
Overwhelming evidence shows us that all species are related–that is, that they
are all descended from a common ancestor
. … Today, we realize that most such resemblances–in both physical structure and embryonic development–are expressions of shared DNA, the direct outcome of a common ancestry.
While orangutans and gorillas are in the great ape family, humans are most closely related to two other species in the family:
bonobos and chimpanzees
.
In a phylogenetic tree, the relatedness of two species has a very specific meaning. Two species are more related
if they have a more recent common ancestor
, and less related if they have a less recent common ancestor.
Generally, the longer ago the last common ancestor lived, the less the organisms have in common. … Scientists can compare the DNA of two organisms;
the more similar the DNA, the more closely related the organisms
.
Are all species related?
Yes
. Just as the tree of life illustrates, all organisms, both living and extinct, are related. Every branch of the tree represents a species, and every fork separating one species from another represents the common ancestor shared by these species.
How do biologists interpret these similarities?
How do biologists interpret these similarities?
By identifying the bones as being homologous and proposing that humans, bats, and dolphins share a common ancestor
.
Homologous structures result from common descent. They are similar in structure but not necessarily similar in function.
Analogous structures
are similar in function but not structure. Analogous structures are not the result of common descent.
Some organisms that appear very closely related on a phylogenetic tree may not actually be closely related. Why is this? In most cases, organisms that appear closely related actually are; however, there are cases where organisms evolved through convergence and appear closely related but are not.
How organisms that are widely different in morphology can have a close evolutionary relationship?
Morphological differences cause organisms to have different structures or body parts. While evolutionary relationships in living organisms can be determined by similarities and differences in DNA sequences, morphological differences are the only traits that can be compared in very old fossils.
What are the similar species with different characteristics?
Convergent evolution
is the opposite of divergent evolution, in which related species evolve different traits. Convergent evolution is similar to parallel evolution, in which two similar but independent species evolve in the same direction and independently acquire similar characteristics.
In general, organisms
that share similar physical features and genomes
tend to be more closely related than those that do not. Such features that overlap both morphologically (in form) and genetically are referred to as homologous structures; they stem from developmental similarities that are based on evolution.
Within that clade the animal with which humans share the most recent common ancestor is the
chimpanzee
. FAMILY TREE of the Hominidae shows that chimpanzees are our closest living relatives.
For example, organisms placed in the
same genus are always more closely related to each other
than those in different genera in the same family, and organisms in the same family are more closely related than those in different orders.
Which organism is your closest relative?
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The chimpanzee and bonobo
are humans’ closest living relatives. These three species look alike in many ways, both in body and behavior.
To determine how closely related two organisms on a cladogram are,
TRACE from the first one to the second one
. The more nodes you pass, the farther apart the organisms are in terms of evolutionary relationship.
Just because species look or behave the same doesn’t mean they are closely related.
Analogous structures
don’t have to share the same evolutionary path. … Analogous structures are not necessarily evidence that two species came from a common ancestor.
Species that have similar ecology could coexist
providing that they have different patterns of habitat use and associations with different environmental variables
. … sellowi was habitat generalist. The use of different habitats can reduce the effect of interspecific competition to levels that allow coexistence.
How do DNA sequences help determine the relationship between species?
Sometimes referred to as
DNA-DNA hybridization
, this process hybridizes the genetic information from two different organisms to determine similarities between them. … Parts where base pairs link back up exhibit genetic similarity. The more information that links up, the closer the species evolutionarily.
How is DNA used for comparison and identification of organisms?
For example, scientists can use DNA sequences
to help determine if they have discovered
a new species. Scientists can also compare DNA sequences from different organisms and measure the number of changes (mutations) between them to infer if species are closely or distantly related.
How does DNA differ between organisms?
DNA is found in nearly all living cells. … Although each organism’s DNA is unique, all DNA is composed of the same nitrogen-based molecules. So how does DNA differ from organism to organism? It is
simply the order in which these smaller molecules are arranged that differs among individuals
.
How do we infer relationships among organisms given the various evidences of evolution?
Similarities between organisms can stem either from shared evolutionary history (homologies) or from separate evolutionary paths (analogies). After homologous information is identified, scientists use cladistics to organize these events as a means to determine an evolutionary timeline.
In that figure, Taxon B and Taxon C are more closely related to one another that either is
to Taxon A
. We know this because Taxon B and Taxon C share a shallower node (the blue node) than then node that either shares with Taxon A (the yellow node).
How does comparative anatomy relate to evolution?
comparative anatomy, the comparative study of the body structures of different species of animals in
order to understand the adaptive changes they have undergone in the course of evolution from common ancestors
. … Homologies of the forelimb among vertebrates, giving evidence for evolution.
Genetic variations that alter gene activity or protein function can introduce different traits in an organism. If a trait is advantageous and helps the individual survive and reproduce, the genetic variation is more likely to be passed to the next generation (a process known as natural selection).
In scientific terms, the evolutionary history and relationship of an organism or group of organisms is called
phylogeny
. Phylogeny describes the relationships of an organism, such as from which organisms it is thought to have evolved, to which species it is most closely related, and so forth.
Which is the best evidence that two species have a common ancestor?
Homologous structures
provide evidence for common ancestry, while analogous structures show that similar selective pressures can produce similar adaptations (beneficial features). Similarities and differences among biological molecules (e.g., in the DNA sequence of genes) can be used to determine species’ relatedness.
Why do related species share homologous traits? -Related species share homologous traits
because they are found in the same geographical area
. -Related species have independently evolved homologous traits. Related species inherited homologous traits from a common ancestor.
That’s because closely related species
most likely diverged from one another fairly recently in the evolutionary span
. Thus, they haven’t had as much time to accumulate random mutations in their genetic codes.
Answer:
Homologous Structures
represent that organissms are similar in functions but does not relate to each other.
Which structures are similar in function but do not indicate that?
Those structures that do not have a common evolutionary origin but are similar in form or function are called
analogous structures
.
Molecular clocks
are used to determine how closely two species are related by calculating the number of differences between the species’ DNA sequences or amino acid sequences. … On the other hand, animals may look similar but can have very different DNA sequences and evolutionary ancestry.
Some organisms that appear very closely related on a phylogenetic tree may not actually be closely related. Why is this? In most cases, organisms that appear closely related actually are; however, there are cases where organisms evolved through convergence and appear closely related but are not.
How can evolutionary relationships among organisms be determined by comparing embryonic development?
This common feature means that all vertebrates evolved from a common ancestor. How can evolutionary relationships among organisms be determined by comparing embryonic development? A
. Embryos retrace their ancestral stages during embryonic development.
