8/7/2019 W3 by Ana G

1/2

Evolution in Extant PopulationsTwo step process:

Variation must exists among individuals

This variations must be heritable

How organisms vary (not all variation is evolution)

Variation in formDifferentiation of parts: different colors, birds have different songs

Ontogeny: development from fertilized egg to mature form. There is a divergence of form

with longer development time among closely related species

Ambystoma tigrinum two morphotypes that have different diets and different behavior,

but same genotype

Growth:

Growth by accretion: adding more of the same (bivalved molluscs, tree rings, corals)

Growth by addition: adding new features (Foraminifera add chambers as they grow, their

coiling is a function of the environment).

Growth by molting: grows in very fast spurts, sheds skin or skeleton arthropodsGrowth by modification: within existing features (epiphyseal growth in mammals)

Isometric growth: only size changes, proportions remain constant

Allometric growth: there is an ontogenic shape change

Sexual dimorphism

Population variation

Geographic variation in deer mouse

Phenotypic plasticity:

nutrition dependent phenotypic plasticity and allometry in some insects

Daphnia longiremis differencence due to presence or absence of predators

Cline: change in particular environmental variable correlates with a variation in aphenotypic character

Rapid Evolution: stickleback body armor and its loss in the absence of predators

Origin of Life

Life

Functional definition: a) process energy separate from environment b) store and process

information c) replication information (reproduction).

Crown group definition: life stems from MRCA of extant organisms.

Reticulate Evolution: horizontal gene transfer (esp in bacteria) endosymbiosis. Createsthe Web of Life

Age of the Earth:

Banded iron formations: indicate photosynthesis by cyanobacteria producing oxygen for

later development of oxygen dependent multicellular life.

Late Precambrian glaciation Snowball Earth

Molecular fossil evidence of origin of life (~3.5by) Bacteria (2.7by), Archaea (2.8by),

8/7/2019 W3 by Ana G

2/2

Eukarya (2.7by).

Stromatolites produced a lot of oxygen, changed concentration in the atmosphere

Readings:

Palumbi- Humans as the worlds greatest evolutionary forceRates of human-mediated evolutionary change sometimes exceeds rate of natural evolution

by several orders of magnitude

Ways of slowing down evolution: drug overkill, direct observation therapy, screening for

resistance before treatment, cycling selection of drugs

Lazcano 2010: Historical Development of Origins Research

Adaptation and Diversification on Islands

Adaptive radiation is the outcome of speciation and adaptation in the context of

ecological opportunity.