Evolution & MorphologyGeneral Zoology, 18 January 2008

Donald Winslow

Readings from Hickman et al. 2008:

Ch. 6 pp 105-113, 115-130, 132-134

Ch. 9 pp 186-190, 192-194

Founders of evolution• Lamarck—inheritance of acquired traits

• Lyell—uniformitarianism & gradualism

• Malthus—exponential growth & limitation

• Darwin—natural selection, speciation

• Wallace—independently developed

theory of evolution by natural selection

& inspired Darwin to publish.

Charles Darwin• Voyage on H.M.S. Beagle, Galapagos

• Natural selection & adaptation– Population growth & limits to growth– Competition and heritable variation– Differential survival & reproduction– Gradual adaptation & speciation

• Reproductive barriers & speciation

Evidence for evolution• Fossil record

– Marine organisms on mountaintops

• Geological time & dating—isotope decay

• Evolutionary trends—horses

• Homology of vertebrate forelimbs (Fig 6.14)

• “Ontogeny recapitulates phylogeny.”– Haeckel

Flying Great Egret (Ardea alba). Photo by Karen Bays.

Bird wings are homologous to a human’s arms.

Ontogeny & phylogeny

• Pharyngeal gill slits

• Paedomorphosis

• Heterochrony

Microevolution

• Population genetics

• Gene pool

• Allele frequencies

• Hardy-Weinberg equilibrium

Forces that change allele frequencies

• Mutation

• Genetic drift

• Nonrandom mating—e.g. assortative mating

• Migration

• Selection (natural, artificial, sexual)– Relative fitness– Stabilizing, directional, & disrupting selection

Bright plumage of male Northern Cardinal—

A result of sexual selection.

Measuring genetic variation

• Protein polymorphism & heterozygosity

• Gel electrophoresis

• Quantitative characters

Dark-eyed Junco (Junco hyemalis) color variants

Macroevolution

• Allopatric & sympatric speciation

• Hybridization, extinction

• Adaptive radiation (diversification)

• Gradualism, punctuated equilibrium

• Mass extinction

• Levels of selection– Genic, individual, kin, group, species

Morphology

• Biological hierarchy

• Grades of organization & body plans

• Describing locations on animal bodies

• Body cavities & germ layers

• Developmental patterns

• Histology

• Body size

Biological hierarchy

• Cell

• Tissue

• Organ

• Organ system

• Organism

• Population

• Community

Nine-banded armadillo

Grades of organization

• Protoplasmic (e.g. protozoa)

• Cellular (e.g. colonial protists, sponges)

• Tissue (e.g. jellyfish)

• Organ (e.g. flatworm)

• Organ system (e.g. molluscs, arthropods)

Luna

moth

Body plans

• Unicellular protists vs multicellular animals– Protozoa vs Metazoa

• Cell-level vs tissue-level organization– Porifera vs Eumetazoa

• Radial symmetry vs bilateral symmetry

• Sac vs “tube-within-a-tube” digestive tracts

• Acoelomate, pseudocoelomate, coelomate

Describing location on animal

• Anterior/posterior

• Dorsal/ventral

• Medial/lateral

• Distal/proximal

• Frontal, sagittal, and transverse planes

Body cavities

• Blastocoel

• Gastrocoel (archenteron)

• Pseudocoel

• Coelom

Germ layers

• Endoderm

• Mesoderm

• Ectoderm

Developmental patterns

• Cleavage—radial or spiral

• Gastrulation (germ layer formation)

• Diploblastic or triploblastic

• Protostome or deuterostome

• Metamerism (segmentation)

Histology

• Blood plasma and interstitial fluids

• Tissues• Endoderm epithelium of digestive tract

• Ectoderm skin & nervous tissue

• Mesodermconnective tissue, muscles, viscera– Connective tissue:

» collagen, blood, lymph, cartilage, bone, fat

Advantages & disadvantagesof large body size

• Predators can subdue larger prey,

• But larger prey can’t hide as easily.

• Larger animals have efficient metabolism,

• But use more energy.

• Larger animals have longer generations.

Humpback whale