Lecture 15: Lamarck and Darwin

Question 1

The Voyage of the Beagle

Answer 1

• 1809: Darwin was born
• 1831: Darwin left Great Britain on the HMS Beagle on a 5 year voyage around the world
• Darwin collected thousands of specimens and observed various adaptions in organisms

Question 2

what was Darwin intrigued by

Answer 2

• the geographic distribution of organisms on the Galapagos Islands
• similarities between organisms in the Galapagos and those in South America
• Oceanic Islands

Question 3

who was Darwin influenced by

Answer 3

geology writings by Charles Lyell and Rev. Thomas Malthus
* Lyell suggested that the Earth is very old and was sculpted by gradual geographical processes that continue today
* Malthus believed that in nature, plants and animals produce far more offspring than can survive and that man too is capable of overproducing if left unchecked. he concluded that unless family size was regulated, man’s misery of famine would become globally epidemic and eventually consume Man.

Question 4

Darwin reasoned that the extended time scale would allow for gradual changes to occur in

Answer 4

• species
• geologic features

Question 5

extended time scale

Answer 5

the concept that evolution occurs over incredibly long periods of time, making significant changes to happen in species slow to come by

Question 6

descent with modification

Answer 6

Darwin made several points in The Origin of Species
* organisms inhabiting Earth today descended from ancestral species
* population increase leads to a struggle for existence, which is linked to the ideas of Malthus

Question 7

natural selection

Answer 7

“Individuals having any advantage, however slight, over others, would have the best chance of surviving and procreating their kind. On the other hand, we may feel sure that any variation in the least injurious would be rigidly destroyed. This preservation of favourable variations and the rejection of injurious variations, I call Natural Selection.”

the mechanism for descent with modification which acts as a hidden hand over eons to provide a unifying theme that interconnects all life forms in the biosphere. evolution follows the laws of nature

Question 8

evidence of evolution

CCOMBF

Answer 8

evolution leaves observable signs:
* the fossil record
* biogeography
* comparative anatomy
* comparative embryology
* molecular biology
* obesity epidemic

Question 9

fossils

Answer 9

imprints or remains of organisms that lived in the past often found in sedimentary rocks

Question 10

fossil record

Answer 10

• the ordered sequence of fossils as they appear in rock layers
• reveals the appearance of organisms in a historical sequence
• fits with the molecular and cellular evidence that prokaryotes are the ancestors of life

Question 11

paleontologists

Answer 11

scientists who study fossils
* have discovered many transitional fossils that link past and present, including evidence that birds descended from one branch of dinosaurs and that whales descended from 4-legged land mammals

Question 12

biogeography

Answer 12

the study of geographic distribution of species
* first suggested to Darwin that today’s organisms evolved from ancestral forms
* Darwin noted that Galapagos animals resembled the species of the South American mainland more than they resembled animals on similar but distant islands

Question 13

comparative anatomy

Answer 13

• the comparison of body structure between different species
• attests that evolution is a remodeling process in which ancestral structures become modified as they take on new functions

Question 14

homology

Answer 14

the similarity in structures due to common ancestry
* illustrated by the remodeling of the pattern of bones forming the forelimbs of mammals for different functions

Question 15

comparative embryology

Answer 15

early stages of development in different animal species reveal additional homologous relationships
* for example, pharyngeal pouches appear on the side of the embryo’s throat, which develop into gill structures in fish and form parts of the ear and throat in humans
* comparative embryology of vertebrates supports evolutionary theory

Question 16

molecular biology

Answer 16

the hereditary background of an organism is documented in
* its DNA
* the proteins encoded by the DNA

evolutionary relationships among species can be determined by comparing
* genes and proteins of different organisms

Question 17

evolution of finches on the Galapagos Islands

Answer 17

Darwin noted the close relationship between adaption to the environment and the origin of new species by observing the Galapagos finches (large ground finch, warbler finch, woodpecker finch)

Question 18

Darwin’s theory of natural selection

Answer 18

Darwin based his theory of natural selection on 2 key observations:
* all species tend to produce excessive numbers of offspring
* organisms vary, and much of this variation is heritable

Question 19

Darwin’s theory of natural selection: observation 1: overproduction and competition

Answer 19

• all species have the potential to produce many more offspring than the environment can support
• this leads to inevitable competition among individuals

Question 20

Darwin’s theory of natural selection: observation 2: individual variation

Answer 20

• variation exists among individuals in a population
• much of this variation is heritable
• natural selection works on the genetic variation that exists within populations. this variation arises as the result of mutations and recombination
• mutations arise as chance events
• what about Mendel? how did Darwin not know about Mendel or Mendel about Darwin? Mendel was obscure, publishing his findings in an obscure journal

Question 21

inference: unequal reproduction success

Answer 21

individuals with traits best suited to the local environment generally leave a larger share of surviving, fertile offspring