Zoology and Evolution

Zoology The scientific study of animals What is an animal?

Evolutionary Tree of Life

Animals Multicellular eukaryotes Heterotrophs (consumers) Develop through a blastula stage Motile at some stage of their life

Choanoflagellate Protozoan Simple colonial flagellates No specialization Precursor to Metazoa

Spherical Colonies of Choanoflagellates Reproduction of the whole cell aggregate through gametes Cell specialization

Animal Kingdom Includes Very Diverse Organisms

Cell level of specialization Porifera

Tissue level of specialization True tissues –Endoderm –Ectoderm Example –Cnidaria

Organ level of specialization Tissues form organs Three germ layers –Ectoderm –Mesoderm –Endoderm Example –Platyhelminthes

Complete alimentary canal Mouth and anus Example –Nematoda

Internal body cavity - Coelom Organs suspended inside body cavity Example –Annelida

Invertebrates – Animals without a backbone

Vertebrates – animals with a backbone

Evolution Process of organic development and change –Continual process – Driven by the environment –Organisms have built in potential for change

Perpetual Change

Common Descent Phylogeny –Common descent through branching lineages Evidence –Homologies – similarity between organism that occur because of common ancestry Structural Genetic

Skeletal Homologies Similarities because of common descent

Skeletal Homologies Similarities because of common function

Evolutionary Relationships Revealed During Embryonic Development

Multiplication of Species Reproductively distinct populations of organisms –Usually but not always differ in form –No interbreeding between species in the wild Species split and develop into new species

Gradualism and Punctuated Equilibrium Gradualism –Small changes accumulate over time –Steady rate of change Punctuated equilibrium –Bursts of rapid change followed by little change –Rate of change varies

Natural Selection

Responses to Selection

Sexual Selection Results in some sexual dimorphism

Potential for Variation

Modern View Microevolution –Small-scale changes –Change within a species Macroevolution –Large-scale changes –Formation of new species