Transcript Chapter 4: The Forces of Evolution and the Formation of Species

CHAPTER 4: THE FORCES OF EVOLUTION
AND THE FORMATION OF SPECIES
HOW NATURAL SELECTION WORKS
• “Natural selection takes the package of traits each
animal or plant inherits from the previous generation
and then alters it in response to the current
environment. Natural selection is not simply about
genes and traits. The environment is the filter through
which traits – and the genes that control their
expression – are selected for or against.”
DARWIN’S FINCHES – THE GOOD AND THE BAD?
KEY TERMS – I.E. EXTREMELY IMPORTANT
TERMS
• Gene flow: movement of genes between populations
• Inbreeding: mating between close relatives.
• Genetic drift: random changes in gene frequency in a population.
• Founder effect: a component of genetic drift theory, statin that new
populations that become isolated from the parent population carry on the
genetic variation of the founders.
• Genetic bottleneck: temporary dramatic reduction in size of a population or
species.
GENE FLOW
GENETIC DRIFT
GENETIC BOTTLENECK
FOUNDER EFFECT
SEXUAL SELECTION
• Sexual selection:
differential
reproductive
success within one
sex of any species.
SEXUAL DIMORPHISM
• Sexual
dimorphism:
difference in size,
shape, or color
between sexes.
CLASSIFICATION AND EVOLUTION
KEY TERMS
• Systematics: branch of biology that describes patterns of organismal
variation.
• Homology: similarity of traits resulting from shared ancestry.
• Analogous: having similar traits due to similar use, not due to shared
ancestry.
• Convergent evolution: similar form or function brought about by natural
selection under similar environments rather than shared ancestry.
• Cladistics: method of classification using ancestral and derived traits to
distinguish patterns of evolution within lineages.
• Cladogram: branching diagram showing evolved relationships among
members of a lineage.
HOMOLOGY AND ANALOGY
CLADOGRAM
WHAT IS A SPECIES?
• Species: an interbreeding group of animals or
plants that are reproductively isolated through
anatomy, ecology, behavior, or geographic
distribution from all other such groups.
• Speciation: formation of one or more new
species via reproductive isolation.
LIGER
A GUIDE TO SPECIES CONCEPTS
• Biological species concept: defines species as interbreeding
populations reproductively isolated from other such populations.
• Evolutionary species concept: defines species as evolutionary
lineages with their own unique identity.
• Ecological species concept: defines species based on the
uniqueness of their ecological niche.
• Recognition species concept: defines species based on
unique traits or behaviors that allow members of one species to
identify each other for mating.
REPRODUCTIVE ISOLATING MECHANISMS
(RIMS)
Any factor – behavioral, ecological, or anatomical – that prevents a male and female of two
different species from hybridizing.
ANAGENESIS AND CLADOGENESIS
• Anagenesis: evolution
of a trait or species into
another over a period of
time.
• Cladogenesis:
evolution through the
branching of a species
or a lineage.
SPECIATION
• Allopatric speciation: speciation occurring via
geographic isolation.
• Paprapatric speciation: speciation occurring when two
populations have continuous distributions and some
phenotypes in that distribution are more favorable than
others.
• Sympatric speciation: speciation occurring in the
same geographic location.
MACROEVOLUTION AND MICROEVOLUTION
GRADUALISM AND PUNCTUATED EQUILIBRIUM
• Gradualism: Darwinian
view of slow, incremental
evolutionary change.
• Punctuated equilibrium:
model of evolution
characterized by rapid
bursts of change, followed
by long periods of stasis.
ADAPTION
• Adaptionism: a premise that all aspects of an organism have been
molded by natural selection to a form optimal fro enhancing
reproductive success.
• Holists would point out that the chin is only the meeting point of the
two halves of the lower jaw, which do not fuse until infancy in human
development. The chin exists because of the position of the teeth, not
because the chin has any adaptive role of its own.
• Reductionism: paradigm that an organism is the sum of many
evolved parts and that organisms can best be understood through an
adaptionist approach.