3 Flashcards
- 1.7 million extant species (existing today) have been described (only ____ of the estimated number)
- For every ______ species, ~100 have gone extinct since beginning of life
- 850 million extant and/or extinct species since the beginning of life!
Biological diversity reflects an interaction between
the forms that preceded them and an ongoing
process of change
All species are _______ : extinction is as much a part of nature as is the formation of new species.
How can we explain this diversity?
- 1.7 million extant species (existing today) have been described (only 1/5 of the estimated number)
- For every extant species, ~100 have gone extinct since beginning of life
- 850 million extant and/or extinct species since the beginning of life!
Biological diversity reflects an interaction between
the forms that preceded them and an ongoing
process of change
All species are temporary: extinction is as much a
part of nature as is the formation of new species.
How can we explain this diversity?
oxford dictionary biology
Darwins definition:
Our working definition in BIOL 243:
Oxford Dictionary of Biology:
The gradual process by which the present diversity of plant and animal life arose from the
earliest and most primitive organisms, which is believed to have been continuing for at
least the past 3 billion years.
Darwin said:
“Evolution” as descent with modification
Results from changes in populations over time
Our working definition in BIOL 243:
Change in allele frequencies in a population over tim
How do we study evolution?
-Genetics:
-Population and quantitive genetics:
-Paleobiology
-Integration of genetics and morphology:
Genetics: how does inheritance work?
* Population and quantitative genetics:
How do allele frequencies change in populations over time and space?
Looking at evolution in real-time….
* Paleobiology:
How do large scale evolutionary changes affect groups of organisms?
* Integration of genetics and morphology: developmental patterns and
evolutionary transition
What are 4 ideas that inspired Darwin
- Some species survive while others go extinct (Cuvier )
– existence of fossilized bones from species that no longer exist - The Earth must be much older than believed, and undergoing change (Lyell )
– landforms form gradually from geological processes, not catastrophes - Species themselves must be capable of changing (Lamarck )
– proposed “transmutation”, mechanism of inheritance of acquired traits roundly dismissed - There must be a pressure to force adaptation, ex. competition for resources (Malthus )
– human populations grow faster than available resources, so “fittest” individuals survive
CUVIER GEORGIS(1769-1832)
- Leading comparative anatomist and palaeontologist of his time
- Found that many species have gone extinct, (he thought in
floods) the number of species were declining - Showed that large bones in USA belonged to extinct mastodon,
not modern elephants
Charles Lyell (1797-1875)
“Principles of Geology” :
Landforms (mountains, valleys, etc.) were not fixed, but
changed slowly as a result of geological processes that
can be observed today (not catastrophes)
* Earth was much older than the accepted ag
Jean-Baptiste Lamarck (1744-1829)
- Believed that species changed over time – transmutation
- Lamarckism: acquired traits can be inherited , lost through
disuse - Started Darwin thinking about the importance of inheritance
- Modern epigenetic research suggests he wasn’t totally wrongJ
Thomas Malthus (1766-1834)
“Principle of Populations”
“Population, when unchecked, increased in a geometrical
ratio and subsistence for man in an arithmetical ratio.”
Human population can increase faster than food supply -
leads to competition for survival
Charles Darwin (1809-1882)
Returned to England in 1837 and began organizing
his sample collection and notebooks
* First ideas about natural selection written in his
notebooks in 1838, but did not publish
* Spent 20 years examining evidence, wanted to ensure
his theory was sound and unassailable
* Other attempts to write on the subject (Robert
Chambers, Patrick Matthew) met with harsh
criticism and threat
Change due to selection - not a new idea
- “Artificial” selection was well understood, from domestication of crops, livestock,
dogs and other pets, etc. - The first chapter of On the Origin of Species is titled “Variation under domestication”
Alfred Russell Wallace (1823-1913)
- Came up with the theory of natural selection
independently of Darwin, but later, in 1858 - Spurred Darwin to publish his own work on
the subject
____________ convinced Darwin that life
evolves
ObservaTIONS
Charles Darwin
On the Origin of Species
by means of natural selection
(November 1859)
The struggle for existence from limited resources
= favourable variations tend to be preserved and
unfavourable ones tend to be destroyed
21
Variation
in traits
Reproductive
Success
Inheritance
Natural Selection
Key Concept
Charles Darwin
On the Origin of Species
by means of natural selection
(November 1859)
The struggle for existence from limited resources
= favorable variations tend to be preserved and
unfavorable ones tend to be destroyed
21
Variation
in traits
Reproductive
Success
Inheritance
Natural Selection
Key Concept
Evolution in response to natural selection is inevitable if:
Evolution in response to natural selection is inevitable if:
–There is variation in a trait
–Variation is heritable
–Some variants survive and reproduce more than others
Specific features of the environment can generate natural
selection on a trait
Darwin noticed species on islands quite ____ together were quite different
from island to island
The closer they were _________, the more similar the species were to
one another
Darwin noticed species on islands quite close together were quite different
from island to island
The closer they were geographically, the more similar the species were to
one another
The Galapagos Islands - Important Considerations
*Located approximately 1100km from the coast
of Ecuador, South America
* Terrestrial species on these islands won’t have
many relatives nearby
* Neighbouring islands will have close relatives
–but new terrestrial species won’t arrive on these islands
from the South American mainland very often
–most of the island species have had plenty of time to
differentiate from their nearest living relatives
* Another way of saying this is that there is very
little gene flow between the islands and the
mainland
Endemic Species of Galapagos Islands
Among the kinds of animals found here and nowhere
else:
– 1 penguin species
– 1 giant tortoise species
– 1 marine iguana species
– 7 species of lava lizard
– 14 species of sea cucumber
– 1 species of sea lion
– 1 species of hawk
– several species each of mockingbirds, doves, owls,
flycatchers, and yellow warbler
Galapagos Finches
Adaptive radiation-
Adaptive radiation - a process in which organisms diversify rapidly
from an ancestral species into many new form
A beak gene?
-Sequences from 120 finches
* Phylogenetic taxonomy similar to phenotypebased taxonomy with a few important differences
suggesting extensive gene flow (hybrid breeding)
* ALX1 gene (encodes transcription factor)
affecting craniofacial development associated
with beak shape
Heritability of gapagalos finches
*It’s important to note that beak size and shape is heritable in these
finches
–A bird with a large, deep beak will have offspring with large and deep beaks
*Natural selection can occur without heritability, but evolution by natural
selection cannot!
In common language, “theory” is used interchangeably for “_____” or
“_______”, and suggests a hesitation to claim as true.
– in science terms, this is more similar to a hypothesis
» A scientific theory is an explanation about some aspect of the
_______ ____
– Incorporates _____ ____ _____ ____ ______ ____ ____ ____
» A scientific theory has stood up to ______ and ________ testing, and
has held ____ every time
In common language, “theory” is used interchangeably for “guess” or
“opinion”, and suggests a hesitation to claim as true.
– in science terms, this is more similar to a hypothesis
» A scientific theory is an explanation about some aspect of the
natural world
– Incorporates substantial evidence, facts, natural laws, and tested hypotheses
» A scientific theory has stood up to constant and repeated testing, and
has held true every time
» Early 19th century European academic societies prohibited participation of
women and ethnic minorities
» Darwin followed “_______” with “___ _____ ____ ____” which attempted to provide a
naturalistic explanation of _______ ________ ________ ______ ________ _______ selection
– took a very __________ and _______ perspective (i.e. white men were the
pinnacle of intelligence and attractiveness)
» ______ ________ to Darwin: “Let the ‘environment’ of women be similar to that of
men and with his opportunities, before she be fairly judged, intellectually his
inferior, please.”
» Early 19th century European academic societies prohibited participation of
women and ethnic minorities
» Darwin followed “Origin” with “The Descent of Man” which attempted to provide a
naturalistic explanation of human morality and intelligence, and sexual selection
– took a very androcentric and Eurocentric perspective (i.e. white men were the
pinnacle of intelligence and attractiveness)
» Caroline Kennard to Darwin: “Let the ‘environment’ of women be similar to that of
men and with his opportunities, before she be fairly judged, intellectually his
inferior, please.”
