This summary is for a first year level biology course. it covers the basics of evolution and the main concepts surrounding evolution and the genetics around it and the main theories that surround this topic.
Descent with Modification, Evolution of Populations
Descent with modification: A Darwin View of Life
Evolution: change in genetic composition of populations from generations
Descent with modification: many species are descendants of ancestral species diff
from modern species.
Explain and connect a vast array of observation of world
Darwinian revolution and traditional views
Scala Naturae and Classification of Species:
Life forms arranged on scale of increasing complexity called Scala Naturae.
Said that God created species therefore perfect
Linnaeus made a classification system, by grouping species into increasingly general
categories.
Similar species= same genus
Same genus=same family
Darwin said that classification based on evolutionary relationships, opposing
Linnaeus.
Ideas about change over time:
Studying fossils (found in sedimentary rocks in aquatic areas)
Strata: new layer of sediment cover old one, get too see which organism was alive
that time. The older the starta, less similar fossils to current life forms.
Paleontology: study of fossils
Cuvier opposed evolution therefore he advocated other principles:
o Catastrophism: in the past events occurred suddenly and were caused by
diff mechanism than ones now.
o Therefore each boundary in starta was a flood
o Catastrophes and immigration caused changes in population.
While other scientists said that change takes place through cumulative effect of slow
but continuous processes
Charles Lyell came up with another principle:
o Uniformitarianism: mechanisms of change=constant over time, same
geological changes from the past are working right now too
Therefore Darwin agreed everything changes in slow, continuous action rather than
sudden events taking in to account the geological changes over the years
Lamarcks Hypothesis of Evolution:
, Provided incorrect mechanism about how evolution occurs
He had two principles:
o Use and disuse: some parts of body used more strongly than others and
those that aren’t deteriorate ( the giraffe example)
o Inheritance of acquired characteristics: organism can pass on these
modifications to offspring.
He also believed that Evolution occurs as organisms become more complex.
His theory is wrong gene traits acquired by one thing used more than the other isn’t
something that can be passed onto offspring.
The one thing that he did recognize that the match of organisms to their
environments is explained by gradual evolutionary change.
Descent with Modification by Natural Selection explain the adaptations of Organisms
and the unity and diversity of life
Darwins focus on Adaptation:
Adaptations: inherited characteristics of organisms that enhance their survival and
reproduction in specific environments. It also causes variation.
Natural Selection: individuals that have certain inherited traits tend to survive and
reproduce than those that don’t.
o Therefore if species move to new environment and natural selection occurs,
could give rise to new species.
o Individuals don’t evolve, populations do over time
o Only work with heritable traits, and if everyone is genetically identical for it,
natural selection won’t occur
Descent with Modification:
The reason organisms share characteristics is because they all descended from a
common ancestor and therefore lived in different habitats, from which they
accumulated diverse modifications, adaptations that let them fit into specific ways of
life.
Can be represented by a phylogenetic tree/ evolutionary tree to see which organisms
are closely related.
Artificial Selection, Natural Selection, and Adaptation:
Artificial Selection: humans modified species by selecting and breeding individuals
that possess desired traits.
Darwin said that a similar process occurs in nature, made two observations and
inferences:
o Observations: population varies in inherited traits
Species reproduce more offspring than they can support therefore they die
o Inferences: individuals that have traits that help them survive and reproduce
leave more offspring than others
Unequal ability of individual to survive and reproduce leads to an
accumulation of favorable traits over generations.
Organisms heritable traits affect how well offspring can cope with environmental
challenges
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