ch 12 Flashcards
Lamarck believed that
evolution occurs as structures develop through use, or disappear through disuse, and that these acquired characteristics are passed to offspring.
Darwin realized that
individuals that have characteristics that give them an advantage in their environments are more likely to survive and reproduce. Thus, these characteristics will increase in a population and over time and the nature of the population will change.
Darwin’s experience in breeding domestic animals, his observations during the voyage of the Beagle and Mathus’s ideas on population led Darwin to develop
the theory of evolution by natural selection.
Darwin did not publish his ideas about natural selection until similar ideas were presented to him by
Alfred Russell Wallace. Today, Darwin’s theory is widely accepted.
Microevolution
is change within a species.
Macroevolution
is change among species.
Although incomplete, the fossil record contains
striking evidence of evolution.
A family tree shows
how organisms are related through evolution. Each branch point in the tree indicates a common ancestor.
DNA and other molecules contain
a record of evolution.
Homologous structures provide evidence of
common ancestry.
Vertebrate embryonic development indicates that
new genetic instructions have been layered on top of older ones.
Gradualism
is the model of evolution in which change occurs gradually over time.
Punctuated equilibrium
is the model of evolution in which change occurs in spurts separated by long periods of equilibrium.
Experiments show that microevolution has occurred within populations of the
European peppered moth.
Balancing selection
maintains an allele in a population when the environment acts on the allele in opposing ways.
Directional selection
causes an allele to become either more or less common.
Lamarck
through use or disuse “acquired characteristics” passed on to generations (1809)
Charles Darwin
at age 22, sails aboard HMS Beagle as unpaid naturalist to collect and study plant and animal specimens, study geology, climate and peoples of the world.
INFLUENCES on voyage:
- Read Lamarck’s theory while sailing. Got him thinking about the “how” of evolution.
- Found: fossils of armadillos that looked similar to present day armadillos
Wondered: Why species in same place similar yet different
Reasoned: One species gave rise to another
• Found: Galapagos plants and animals similar to nearby South America AND not similar to other similar but distant tropical island species.
Wondered: Why wouldn’t a divine creator create similar species on ALL similar tropical islands around the would ? Why Galapagos species resembled nearby South American species instead?
Reasoned: They migrated from nearby SA and then evolved due to different conditions of the different islands.
INFLUENCES at home:
• Read Thomas Malthus’s paper.
Thomas Malthus’s points:
Unchecked, a human population would grow at geometric rate while food supply would grow at
arithmetic rate.
Darwin realizes Malthus’s principle applies to all species – every organism has potential to have offspring BUT not all do because of pressures.
• Ran his family’s farm - farmers “artificially” select which organisms in this year’s crops or herds will get to live & reproduce (to pass on the traits the farmer wants).
Elements of Natural Selection:
- Must have: Phenotype variation in a population - if all members of a population are the same then none will have worse (or better) traits than others.
- Must have: A NEW pressure selects “for” or “against” certain traits - if there is no new/different pressure than there’s no reason a population will change
- These two “must have” conditions result in: Those with better traits survive because they have better traits….
- …which results in: those that survive get to reproduce (in larger numbers than those that don’t survive as well)…..
- …which results in: those that survive and reproduce and, therefore, pass on their (better) traits to the next generation.
Variation
exists within genes of every species.
In a specific environment some individuals of a species are better suited to
survive and breed.
New species
replace old species over time.
Fossil evidence shows clearly that
species living today evolved from earlier species.