Ch 7 Review Flashcards
What were two prevailing ideas about the
natural world prior to the 1800s?
1) Species were immutable (fixed, don’t change)
2) Earth is young + relatively unchanging (less than 10,000 yrs old)
What observations from geology and fossils
caused people to question these ideas?
geology:
Hutton concluded that it must have taken millions of years, not thousands, to form the current landscape. His evidence supported the theory of uniformitarianism, which stated that Earth was formed entirely by slow-moving processes, such as erosion and sedimentation, and that these slow forces continue to shape the landscape
fossils:
Cuvier concluded that the mammoth’s skeleton was
different enough from an elephant’s that mammoths had to be considered a different species and that the mammoth had become extinct. The discovery of dinosaur fossils, such as the T. rex, was also evidence that some organisms became extinct long ago
Explain what is meant by the term “evolution,”
and give an example.
-idea that all species are descendants of ancient species that were different from modern-day species.
e.g. whales evolved from land dwelling animals with
4 limbs
-biological history of life on Earth, from the earliest micro-organisms to the diversity of modern-day organisms
Explain Lamarck’s hypothesis of
“inheritance of acquired characteristics.”
Lamarck believed that individuals could pass down characteristics they acquired during their lives
-e.g. if an adult giraffe stretched its neck during its lifetime, then its offspring would be born with slightly longer necks.
What was the weakness of his hypothesis on the inheritance of acquired characteristics?
Lamarck incorrectly theorized that offspring inherit acquired traits from their parents
-he did not know how traits were inherited & that the organism’s behaviour has no effect on its inherited characteristics
How does natural selection lead to adaptation?
-The idea of natural selection is that traits that can be passed down allow organisms to adapt to the environment better than other organisms of the same species.
Provide examples for each of the following
observations Darwin made on his journey on
the Beagle.
(a) Species vary globally
-unrelated species look/behave similarly if they occupy similar environments
ex. African ostrich, South American rheas and Australian emus
-some organisms are unique to certain areas
ex. kangaroos/marsupials only in Australia
Provide examples for each of the following
observations Darwin made on his journey on
the Beagle.
(b) Species vary locally
-organisms that occupy different habitats, look different
ex. Galapagos Islands
-different turtles on different islands that are adapted to feed differently, depending on available vegetation/geography
-darwin’s finches had differently shaped bills according to their feeding patterns
Provide examples for each of the following
observations Darwin made on his journey on
the Beagle.
(c) Species vary over time.
glyptodon evolved into armadillo
(a) What is meant by the term “variation”?
Variation refers to differences among
members of the same species
(b) List some variations in hares.
The jackrabbit has fur that blends well in the desert and ears that help cool its body.
The snowshoe hare has white fur that provides protective camouflage in snowy northern regions.
(c) Why are variations important in a species?
-necessary for the survival of species as variation makes species more adapted to survive and grow in the changing environmental conditions
-helps the species overcome the adversities of extreme conditions in their surroundings
-can survive better and reproduce to pass the genes to the offspring
Define “fitness.” Give an example of how
the environment can influence the fitness of
individuals in a species
-organism’s ability to survive and reproduce in its specific environment
the more suitable an environment is for an organism’s phenotype, the higher the organism’s fitness level
-e.g. green crickets blend into grass, but yellow crickets don’t, so birds will eat the yellow crickets.
-green crickets have a higher level of fitness since they survived and can reproduce
Natural selection vs. Artificial selection
Natural selection is any selection process that occurs as a result of an organism’s ability to adapt to its surroundings. Basically, the environment “chooses” the favourable trait.
Artificial selection, is selective breeding that is imposed by an external entity, usually humans, in order to enhance the frequency of desirable features. Basically, humans choose the traits they want when breeding an organism.
How did Darwin explain the similarities
between flightless birds on different
continents?
explained with his “species vary globally” observation from his voyage
-unrelated species look/behave similarly if they occupy similar environments
ex. African ostrich, South American rheas and Australian emus
How did he explain the finch species
he found on the different islands of the
Galapagos?
“species vary locally” observation
-organisms that occupy different habitats, look different
-initially, he thought these birds were from different bird families because they looked different from one another
-but when he examined them more closely, he found they were all finches
-each species was adapted to feed on the particular food sources on its home island
What are vestigial structures?
remnants of structures that may have had important functions in an ancestral species but have no clear function in some of the modern descendants
How do the vestigial structures in modern
whales help us understand whales’
evolutionary history?
-The fossil record of whales shows how whales’ hind limbs became vestigial.
-Modern whales lack hind limbs, but some have small vestigial hip bones
-Tells us that was probably derived from their
four-footed ancestors and whales were evolved from land animals
How can comparing amino-acid sequences
between species help establish evolutionary
relationships?
the more amino acids that match up, the more closely related the two species will be
-e.g. humans(0) are more closely related to primates(1) than to other vertebrates
The peppered moth, Biston betularia, occurs
in two forms: a grey mottled form, and a dark
form. These moths like to rest on tree trunks.
A biologist named H.D. Kettlewell observed
that lighter grey forms suffered higher mortality
in areas where there were more coal-burning
factories.
(a) How would Lamarck explain this
observation?
-he would use his principle of “tendency towards perfection”
-Organisms continually (willingly) change and acquire features in order to be more successful in their environments
-he would say that the grey moths would turn dark in order to adapt to their environment and stay alive
The peppered moth, Biston betularia, occurs
in two forms: a grey mottled form, and a dark
form. These moths like to rest on tree trunks.
A biologist named H.D. Kettlewell observed
that lighter grey forms suffered higher mortality
in areas where there were more coal-burning
factories.
(b) How would Darwin explain this
observation?
Natural Selection
-Process by which individuals with inherited characteristics well suited to their environment leave more offspring on average than do individuals with adaptations less suited to the environment
-he recognized that the camouflage of the light moth no longer worked in the dark forest.
-grey moths were being killed + couldn’t reproduce
-dark moths live longer in a dark forest, so they survived and had more time to breed
-dark moths were “favoured” by the environment over
grey moths
Does evolution make organisms “better”?
Sometimes…
-traits are passed down to allow organisms to adapt to the environment better than other organisms of the same species
-this enables better survival and reproduction compared with other members of the species
-natural selection gets rid of a lot of “unfavourable” species but produces organisms perfectly suited to their environments
-On the other hand, it’s perfectly possible for a change that is worse than useless to spread through a population, which isn’t beneficial for organisms
For each of the following adaptations, decide
what aspect of the organism’s environment
played a role in the development of the
adaptation and explain the process of natural
selection that led to the adaptation.
(a) fat storage humps in camels
-camels live in the desert, where it’s very hot and there’s less food and water
-the humps minimize heat insulation + helps them to stay cool
-humps also store fat that they can eat when food is scarce
-process of natural selection: camels without humps most likely died while camels with humps survived and reproduced (survival of the fittest), making most of the camel population over time have humps
-fat storage humps “favoured” by environment
For each of the following adaptations, decide
what aspect of the organism’s environment
played a role in the development of the
adaptation and explain the process of natural
selection that led to the adaptation.
(b) “white” fur in polar bears
-have white fur to camouflage in their environment
-process of natural selection: bears that weren’t white most likely got eaten by predators, white polar bears survived and reproduced (survival of the fittest), most of the polar bear population now has white fur
-white fur “favoured” by environment
For each of the following adaptations, decide
what aspect of the organism’s environment
played a role in the development of the
adaptation and explain the process of natural
selection that led to the adaptation.
(c) a kangaroo’s marsupial pouch
-pouch is for carrying the babies and letting them nurse
-process of natural selection: early marsupials nested their young, but the environment “favoured” the development of a pouch to keep them in
For each of the following adaptations, decide
what aspect of the organism’s environment
played a role in the development of the
adaptation and explain the process of natural
selection that led to the adaptation.
(d) stripes on zebras
-black stripes would absorb heat in the morning and warm up zebras, whereas white stripes reflect light more and could thus help cool zebras as they graze for hours in the blazing sun
natural selection: zebra’s without stripes most likely died, striped zebras survived and reproduced(survival of the fittest), most of the zebra population now has stripes
-environment “favoured” striped zebras
Maiacetus is found in Pakistan and is believed to be an ancestor of modern whales.
(a) What features of this fossil are more suited
for a terrestrial habitat?
-4 limbs
-tail
-sharp teeth
Maiacetus is found in Pakistan and is believed to be an ancestor of modern whales.
(b) What features connect it to modern whales,
which live in an aquatic habitat?
-2 limbs look like they were used for swimming
-wide rib cage
-hind legs too small to support a lot of weight, so had
to be aquatic
Form a hypothesis to explain the observation
that animals and plants of India are almost
completely different from the species found in
nearby Southeast Asia
geographic distribution- closely related but different
-all descendants of a single ancestral species from the mainland
-became geographically isolated on the different islands and developed adaptations that were best suited for the local environment on each island
-however different they now look, are all descended from the same ancestral species
How do weather patterns affect the evolution
of finches in the Galapagos Islands?
wet years - smalls seeds are abundant, large and small beak finches can both eat them
dry years - mostly large seeds, only finches with large beaks can eat them, small beak finches die from no food
-therefore, large beaked finches would be favoured in natural selection (survival of the fittest) and most of the finch population would have large beaks.
Compare the structural similarities between
a bat’s wing, a human’s arm and a whale’s
flipper
-consist of the same skeletal parts
-all have the same basic combination of bones
-these different types of limbs move each animal in a different way
How is the limb in each of the cases
above (bat’s wing, a human’s arm and a whale’s
flipper) structurally modified to perform its
function?
Similar structures in species that share a common ancestor are called homologous structures.
Structures that originally functioned one way in ancestral species become modified as they take
on new functions.
