Evolution 1 Flashcards
What is evolution? What does it encompass?
Evolution is a change in the genetic composition of a population over successive generations. Includes:
Descent with modification
Change over periods of time
Variety between individuals in a species
Variety between species
What are the theories of gradualism and uniformitarianism?
Gradualism and uniformitarianism were thought up by James Hutton and Charles Lyell
The idea was that Earth can only change slowly, and thte uniform, constant change of our planet could be a model for the change in species
Fossils had indicated that species had gone extinct and changed previously
What is the theory of catastrophism?
Thought up by Georges Cuvier
The idea that changes on Earth could, at times, be fast and drastic, such as in earthquakes and volcanoes
Local changes can be much faster than global changes
The strata of Earth were coherent with successive catastrophes, proven by fossils found in each layer
Geirges Buffon did what?
Geirges Buffon laid down the groundwork for the theory of evolution.
Geirges Buffon studied animals body structure
He noticed that some animals have structures in their bodies which are not useful
E.g., pigs have extra toes which do not reach the ground
His theory was that, in the past, pigs might’ve used these digits, but now no longer need them.
Information about the HMS Beagle Voyage
Between 1831 - 1836
Gave Darwin the opportunity to extensively research organisms and fossils worldwide
The Galapagos Islands:
Unique organisms forced Darwin to think about their origins
Only inhabited by birds and reptiles
Who came up with “struggle for existence?” What is it?
Thomas Malthus
If left alone populations grow exponentially, but no single species is overruning the Earth
Limited resources mean those who obtain them are most fit to survive
Not necessarily the traits which are strongest, just the ones which are most efficient
What is “Use or Disuse” theory? Who came up with it?
Jean Baptiste de Lamarck
“Use or Disuse” determines which traits would become prominent
Change could come by a wanted or perceived need
Giraffe example: Giraffes gained their long necks by willing them into existence after a shortage in ground foliage.
This theory is not correct with the addition of the last point
Although incorrect, this theory included the important detail of traits being heritable, which aided in the discovery of evolution theory.
What is natural selection?
Natural selection is the way in which nature favours that reproductive success of some individuals over others; The survival of those most fit to live in an environment because of their specific traits. Formulated by Darwin, rests on three principals
What are the three principals of natural selection?
- Natural Variation
- Reproductive Success
- Environmental Influences
Natural variation.. (Natural Selection)
There must be variations in organisms, otherwise all organisms will be equally matched and nothing will be favoured.
Variation is caused by genetic mutations, and can be advantageous, disadvantageous, or neutral.
Without an environmental context, you can’t establish the value of a given variation.
(Natural selection is less important in a day to day human life because we have created technologies to correct our disadvantages).
Reproductive success.. (Natural Selection)
Reproduction is furthering the success of a species because it is increasing genetic variation.
Organisms are reproductively successful if they survive to the reproductive age, can attract a mate, and can produce viable offspring.
This is important because, without reproductive success, no species would be able to survive past the first generation.
Favourable traits lead to reproductive success.
Environmental influences.. (Natural Selection)
The favourablility of traits depends on many environmental factors, including other organisms, resource scarcity, climate, etc..
Sexual selection
Species with sexual dimorphism, which means there are drastic differences in appearance or behaviours between males and females. This is often seen in the colours of birds.
Often means the males compete and the females choose a mate
Kin selection
Species with very strong social structures, such as wolves and meerkats
Can jeopardize their own reproduction/exclusive fitness and survival to help their kin survive
Artificial selection
Domestic species
In this form of selection, humans are the selective agents
Traits we choose are not always advantageous to the organism, but they get passed on because they are selected by people
Cast vs Impression fossils
Impression fossils:
Impression fossils form when an organism dies. Before entirely decomposing, it is covered in silt, mud, or ash.
The flesh then decomposes inside of this casing, leaving minerals in a ‘negative imprint’
Certain parts of the organism may mineralize
Cast fossils:
Cast fossils start the same, with a dead organism cast in silt, mud, or ash. However, large or tough structures, such as bones, remain after the decomposition of the flesh.
Over time, minerals seep in and replace the bones
The new remains are now petrified, or ‘made of stone.’
These fossils are really only rocks shaped like organisms
How are fossils evidence for evolution?
Fossils can tell us about change over time. Different fossils are found in different strata or materials, telling us that they happened over different time periods.
The problems of fossil evidence
Fossilization needs a specific set of conditions to occur. If things do not fossilize, we won’t have any record of them.
Incomplete or fragmented fossil records, which are inconsistent over different strata. Why do some strata have many fossils, while others have none?
If there is only one or two fossils found for a certain species, does it accurately represent the whole?
Analogous vs Homologous vs Vestigial
Analogous structures = Same use, different structures
Homologous structures = Similar structures, different uses
Vestigial structures = Present structures which have lost function
Embryology
Vertebrate embryos all start out very similar, then diverge in form. The longer similarities last between any two embryos, the more closely related the two organisms are.
In Darwin’s time, it was thought that embryonic development was a form of mini-evolution.
“Ontogeny Recapitulates Phylogeny” means that the development of an embryo imitates the evolution of that organism/species. In other words, each embryonic stage represents an evolutionary milestone in that organism, and imitates their ancestors.
If members of phyla evolved from a common ancestor, then their embryology should be similar
