Macroevolution #15 Flashcards
Describe how new forms of life evolve.
New forms of life evolve through the co-option of traits towards new functions, which involves many intermediate steps. Traits in modern species evolved long before the modern species that are using them.
Understand how novel traits evolve.
Novel traits can evolve through permissive conditions, freedom from constraint, facilitated variation, substitution, and the use of homologous structures in new ways.
Discuss major trends in macroevolution.
Major trends in macroevolution include rates of evolution, phylogenetic conservatism, and gradualism vs. punctuated equilibria.
What is macroevolution?
Macroevolution is evolution above the species level that involves evolutionary changes among populations leading to reproductive barriers, eventually leading to speciation.
How have rates of evolutionary change differed over time?
Rates of evolutionary change have varied depending on the character being studied, within and between lineages, and over different time intervals. Rates depend on the direction of selection, phylogenetic conservatism, and phylogenetic niche conservatism.
What is the explanation for gaps in the fossil record?
The extinction of intermediate forms is one explanation for gaps in the fossil record.
What is gradualism?
Gradualism is the idea that evolution proceeds gradually, with modest jumps between different species connected by intermediate forms.
What is saltation?
Saltation is the idea that rare major mutations (macromutations) can give rise to new species, but it is unlikely. Big jumps in evolution are possible, but too big a jump can lead to decreased survival.
What are some examples of large-effect mutations/alleles?
Bristle number in Drosophila, mimicry phenotypes in Heliconius, and regulatory Hox genes can accumulate changes gradually and have large morphological outcomes.
What is phylogenetic conservatism?
Phylogenetic conservatism is the tendency for traits to be conserved over time within lineages, which can be due to stabilizing selection, internal constraints, and phylogenetic niche conservatism.
What is punctuated equilibria?
Punctuated equilibria is the idea that long periods of little morphological change are punctuated by short abrupt changes. This hypothesis is not widely accepted but stimulated interest in the field.
What are some associated features characteristic of mammals?
Posture, tooth differentiation, skull and jaw changes, secondary palate, and brain size are some associated features characteristic of mammals.
What are some examples of homology?
False fingers in giant pandas and moles are examples of using homologous structures in new ways.
