The History Of Evolutionary Thought

Question 1

What was the view of Plato?

Answer 1

For Plato, each living thing was a perfect representation of an ideal form, which was perfect and immutable. For every type of organism, you can imagine the “ perfect” example of that organism—the perfect platonic form. If you looked at that type of organism in detail though, you’d find a lot of variation and that individuals differed from that perfect example in some way. For Greeks, this variation was of no interest and represented imperfection.

Question 2

What was the view of Aristotle?

Answer 2

Aristotle suggested “ the great chain of being” and this became part of Christian theology. The idea is that there’s a scale. From the most advanced to the most primitive. Humans were at the top ( although angels were higher) and below humans were the simplest organisms, such as worms and then rocks.

Question 3

Was there a time dimension to Aristotle’s views?

Answer 3

There was no time dimension—I.e the idea that that organisms could move up or down the scale. It was fixed top to bottom scale.

Question 4

What did Aristotle call his scale?

Answer 4

Scala naturae. Life forms could be arranged on a ladder, or scale of increasing complexity. Each form
Of life, perfect and permanent had its allotted rung on the ladder.

Question 5

How were these ideas consistent with the Old Testament account of creation?

Answer 5

Because it states that species were individually designed by God and therefore perfect. In the 1700s, many scientists interpreted the often remarkable match of organisms to their environment as evidence that the creator had designed each species for a particular purpose.

Question 6

Describe the work of Linnaeus

Answer 6

Linnaeus sought to classify life’s diversity “ for the greater glory of God”. Linnaeus developed the two part, or binomial format for naming species ( such as Homo sapiens for humans) that is still used today. The binomial system of classification.

Question 7

How does Linnaeus differ to Aristotle?

Answer 7

Instead of the linear hierarchy of the scala naturae, Linnaeus adopted a nested classification system, grouping similar species into increasingly general categories. For example, similar species are group in the same genus, similar genera ( plural of genus) are grouped in the same family and so on.

Question 8

What is the important thing to remember about Linnaeus’s classification?

Answer 8

Linnaeus did not put down the resemblance among species to be due to evolutionary relationships ( I.e having evolved from the same common ancestor), but rather to the pattern of their creation.

Question 9

What did Darwin noticed about scientists who used the Linnaean classification system?

Answer 9

Darwin argued that classification should be based on evolutionary relationships. He noticed that scientists using the Linnaean system often grouped organisms in ways that reflected those relationships anyway.

Question 10

What’s the important thing to remember about evolution?

Answer 10

The idea of evolution was established well before Darwin—I.e Lamarck.

Question 11

What is Lamarck remembered for?

Answer 11

He’s not remembered for his visionary recognition that evolutionary change explains patterns in fossils and the match of organisms to their environment, but for the incorrect mechanism he proposed.

Question 12

How did Lamarck arrive at his hypothesis?

Answer 12

By comparing living species with fossil forms, he found what appeared to be several lines of descent, each a chronological series of older to younger fossils leading to a living species.

Question 13

How did Lamarck explain this evolution? What were the two principles?

Answer 13

Use and disuse: the idea that parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate. Among many examples, he cited the giraffe stretching its neck to reach leaves on high branches. The second principle, inheritance of acquired characteristics, stated that an organism could pass on these modifications to its offspring. Lamarck reasoner that the long, muscular neck of the living giraffe had evolved over many generations as giraffes stretched their necks even higher

Question 14

Why else did Lamarck think evolution occurred?

Answer 14

He thought evolution occurred because organisms have an innate drive to become more complex.

Question 15

Where did Darwin draw some of his source of information from?

Answer 15

He drew from the work of scientists studying fossils ( the remains or traces of organisms from the past).

Question 16

Where are many fossils found?

Answer 16

They are found in sedimentary rocks formed from the sand and mud that settle to the bottom of seas, lands and swamps. New layers of sediment cover older ones and compress them into super imposed layers of rock called strata( singular, stratum)

Question 17

How can stratum provide a history of life?

Answer 17

Rivers carry sediment ( sand and mud) into aquatic habitats such as seas and swamps. Over time, sedimentary rock layers ( strata) form under water. Some strata contain fossils. It provides a glimpse of some of the organisms that populated the earth when the strata formed .As water levels change and geological activity pushes layers of rock upward, the strata and their fossils are exposed. Later erosion may carve through upper ( younger) strata, revealing deeper (older) strata that had been buried.

A stratum is a layer of sedimentary rock or soil

Question 18

What was Cuvier’s contribution?

Answer 18

Cuvier noted that the older the stratum, the more dissimilar its fossils were to current life-forms. He also noticed that from one layer to the next, some new species appeared while others disappeared. He inferred extinction must have been a common occurrence but he staunchly opposed the idea of evolution. Cuvier speculated that each boundary between strata represented a sudden catastrophic event, such as a flood, that had destroyed many of the species living in that area. Such regions, he reasoned, were later repopulated by different species immigrating from other areas.

Question 19

Who developed palaeontology ?

Answer 19

Palaeontology, the study of fossils, was developed in large part by Cuvier. He essentially founded. The science of competitive anatomy. His theory was called “catastrophism”. Catastrophism states that natural history has been punctuated by catastrophic events that altered that way life developed and rocks were deposited.

Question 20

What were Lyell’s views?

Answer 20

Lyell wrote Principles of Geology (1830) in his Uniformitarianism - “ the present is the key to the past” . He did not accept the idea of evolution in 1830, but was later convinced by the arguments of Darwin.

.Lyell argued that the formation of the Earth’s crust took place through countless small changes occurring over vast periods of time, all according to known natural laws. Lyell wrote that the same geological processes are operating today as in the past, and at the same rate.

So in contrast to Cuvier’s emphasis on sudden events, other scientists suggested that profound change could take place through the cumulative effect of slow but continuous processes

Lyell thought of new species being created in terms of ecosystem roles. A new species of carnivore could not be created unless and until a suitable prey species was already in place

Question 21

How did Lyell influence Darwin’s thinking?

Answer 21

Darwin agreed that if geological Change results from slow, continuous actions rather than from sudden events, then the Earth must be much older than the widely age of a few thousand years. It would, for example, take a very long time for a river to carve a canyon by erosion. He later reasoned that perhaps similarly slow and subtle processes could produce biological change ( evolution)

Question 22

Describe Darwin’s early life

Answer 22

• Dropped out of Edinburgh medical school
• Enrolled at Cambridge to be a clergyman
• Skilled naturalist

Question 23

Describe Darwin’s work on the HMS beagle (1831-36)

Answer 23

The primary mission of the voyage was to chart poorly known stretches of the South American coastline. Darwin, however, spent most of his time on shore, observing and collecting thousands of plants and animals.
He described features of organisms that made them well suited to such diverse environments as the humid jungles of Brazil, the expansive grasslands of Argentina etc.
He also noted that the planet and animals in temperate regions of South America more closely resembled species living in the South American tropics than species living in temperate regions of Europe. Furthermore, the fossils he found, though clearly different from living species, resembled the living organisms of South America

Question 24

Give a bit more detail about Darwin’s findings on the HMS beagle

Answer 24

In 1832, as Beagle was exploring Bahia Blanca along the coast of Argentina, Darwin discovered the bones of fossil mammals at two localities. In a place where armadillos were abounded, he was especially struck by what looked like the outer shell of an extinct form of armadillo.

In another location, he found the bones of extinct giant ground sloths ( Armadillos and sloths belong to the Order Edentata, a primitive group of mammals restricted to the South American continent). Why would fossil remains and modern species found on the same continent resemble each other so closely he wondered?

Question 25

What did the diverse evidence from the mammalian fossil record cause Darwin to think?

Answer 25

He began to speculate about the causes of extinction and paid special attention to endemic species. By focusing on endemic species, he was eliminating the possibility they migrated from elsewhere. Whatever had happened to put new replacement species in place had occurred right there in South America.

Question 26

Describe Darwin’s findings on the Galapagos

Answer 26

On the Galápagos Islands he was particularly impressed by finches, who occupied what we would bake call different ecological niches. Darwin observer that the finches on the Galápagos Islands were all very similar to a single type of finch found on mainland South America. However, the Galapagos finches were also very different from the mainland species and each other. The finches on each island had a distinct variation in overall size, beak shape, claw size etc— which were determined by their food source . Some birds had long, thin beams and sharp claws conducive for eating insects and others had large, powerful beaks for cracking open nuts.

Question 27

Describe Darwin’s geology

Answer 27

On the South American mainland the fossils were obviously related to smaller species found extant in South America specifically

Darwin read “Lyell’s principles of geology” during the voyage. He experienced geological change firsthand when a violent earthquake shook the coast of chile, and he observed afterward that rocks along the coast had been thrust up by several meters. Finding fossils of ocean organisms high up in the Andes, Darwin inferred that the rocks containing the fossils must have been raised there by many similar earthquakes. These observations reinforced what he had learned from Lyell: Physical evidence did not support the traditional view that the Earth was only a few thousand years old

Question 28

Describe more on Darwin on the Galapagos

Answer 28

The Galapagos areva group of volcanic islands located near the equator about 900 km west of South America. Darwin was fascinated by the unusual organisms there. The birds included several types of mockingbirds. These mockingbirds, although similar to each, seemed to be different species. Some were unique to individual islands, while others lived on two or more adjacent islands. Furthermore, although the animals on the Galápagos resembled species living on the South American mainland, most of the Galápagos species were not known from anywhere else in the world. Darwin hypothesised that the Galápagos had been colonised by organisms that had strayed from South America and then diversified, giving rise to new species on the various islands.

Question 29

What did Darwin realise from adaptations?

Answer 29

During the voyage of the beagle, Darwin observed many examples of adaptations, inherited characteristics of organisms that enhance their survival and reproduction in specific environments. Later, as he reassessed his observations, he began to perceive adaptation to the environment and the origin of new species as a closely related processes.
Could a new species arise from an ancestral form by the gradual accumulation of adaptations to a different environment? From the studies made years after Darwin’s voyage, biologists have concluded that this is indeed what happened to a diverse group of finches found on the Galápagos Islands. The finches’ various brand and behaviours are adapted to the specific foods available in their home islands. Darwin realised that explaining such adaptations was essential to understanding evolution. His explanation of how adaptations arise centred on natural selection ( a process in which Individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits).

Question 30

Describe the influence of Malthus

Answer 30

Darwin was influenced by Lyell, but also by Thomas Malthus, who wrote “ essay on the principle of Population” in 1798, about the consequences of expanding populations