Test 2 Flashcards
Explain common descent, common ancestor, and what we now realize it’s due to
Darwin saw evidence that all organisms had similar anatomical structures. This was because they all had a common ancestor. Today we realize that this is specifically due to shared DNA which is a result of a common ancestor.
Give an example of common descent
Pentadactyl limb-adapted by modification. 5 fingered limb.
Monkeys being able to grasp
The difference in shape and function of the mammalian limb bones is due to gradual modifications that made the organism better able to survive in a particular environment. Environmental factors naturally select for or against variations in the basic shape of bones-gives evolutionary advantage. There is a genetic basis to this (Darwin didn’t know in his time)
Descent with Modification
Natural selection selects among whatever genetic variations arise due to ___
Random mutation
Why is natural selection not random?
The genetic variation that occurs in a population because of mutation is random, but selection is not because selection acts on that variation in a very non-random way: genetic variants that aid survival and reproduction are much more likely to become common than variants that don’t.
Summarize Darwin’s theory
Individuals with the variations/adaptations best suited to their environment will survive and reproduce. Those not suited will be less likely to breed (survival of the fittest). There is a
genetic basis! These variations are due to random genetic mutation. * Species change over time by passing on their useful (and harmful?) traits to their offspring*
All species alive today have ___ from ancient ancestors. Ultimately, all organisms on earth are united into a single ___
Descended with modifications; tree of life
The concept that a group of closely related species are all descended with some modifications from the same ancestor
Common ancestry
Idea that living species have descended with changes due to adaptations and natural selection from species that lived before them
Descent with modification
What is one piece of evidence for common ancestry/descent with modification?
Fossils are evidence that the world was much older than once thought. They show how organisms have changed over time. 99% of species that once lived are now extinct.
Preserved remains or traces of ancient organisms
Fossils
Fossil record: when comparing fossils found in rock layers, the ___ the layer the ___ the fossil
Deeper; older
What is more evidence of evolution?
Biogeography. Shows how closely related species change in different environments/selection pressures and shows how distantly related groups have evolved similar traits under similar selection pressures
The study of where species live now and where species and their ancestors lived in the past. Shows common ancestry in two ways: 1) how closely related species change in different environments/selection pressures; 2) how distantly related groups have evolved similar traits under similar selection pressures
Biogeography
The study of similar characteristics between organisms. Three major branches: anatomical, embryological, molecular
Homology
What is the 3rd piece of evidence of common ancestry?
Homology
Published On the Origin of Species in 1859. Introduced the theory of evolution via natural selection
Charles Darwin
Same structure, different function; same ancestor, different function. Give an example.
Homologous structures. Example: human hand, bat’s wing, and whale’s flipper are all the same structure
Structures similar in function, but not inherited from a common ancestor. Same function but evolved from different places. Give an example.
Analogous structures. Example: butterfly wing and bird wing
How are analogous structures also evidence for evolution?
They show that 2 organisms that came from different ancestors when placed under the same environmental pressures can evolve the same adaptations
The study of developing animals in their earliest stages. Evidence for evolution because many different organisms have embryos that look alike suggesting they evolved from a common ancestor
Embryology
All living things contain DNA and RNA. Changes in proteins, DNA, and RNA, can be traced from ancestors to their descendants. The fewer differences there are between these molecules in different organisms, the more closely related they are.
Molecular Homology
DNA % overlap of a dog with a chimpanzee
54%
DNA % overlap of a cat with a chimpanzee
47%
DNA % overlap of a gorilla with a chimpanzee
87%
DNA % overlap of a human with a chimpanzee
97%
DNA % overlap of a giraffe with a chimpanzee
68%
shows that everything comes from common ancestor and shows how closely related species are
Phylogenetic tree
The outer portion of the kidney
Renal cortex
Inner portion of kidney
Medulla
What are the 3 primary tissue layers that form in the embryo, from which all other tissues develop?
Endoderm
Ectoderm
Mesoderm
What are the two types of striated muscle tissue?
Skeletal and cardiac
In humans, the thigh is ___ to the foot
Proximal
In humans, the head is ___ to the tail
Anterior
The ___ carry oxygen rich blood to the fetal pig from the mother
Umbilical veins
True or false: mammary papillae are present only in female pigs
False
What are the four tissue types?
Epithelial
Skeletal
Muscle
Connective
Name 3 pieces of evidence for evolution/common ancestry
Fossils
Biogeography
Homology
