Animal Evolution and Diversity

egan lecture 21

How do we differentiate the multicellular kingdoms?

Into plants (autotrophic), fungi (absorptive heterotrophs), and animals (ingestive heterotrophs)

What cell structure are animals?

multicellular eukaryotes

How are animal cells supported?

by structural proteins such as collagen than cell walls

What tissues are unique, defining characteristics of animals?

nervous and muscle tissue

What are tissues?

they are composed of an integrated group of cells with a common structure, function, or both

What four tissues do complex animals have?

epithelial, connective, muscle, nervous

How do animals reproduce?

they reproduce sexually, with the diploid stage usually dominating the life cycle

How are sperm and egg cells produced?

directly by meiotic division in animals

What is cleavage?

a succession of cell division without growth between divisions

What does cleavage lead to?

formation of a blastula

What is a blastula?

an early stage in animal embryonic development when it is a hollow ball of cells (blastomeres)

What happens to the blastula?

it will undergo gastrulation, forming a gastrula with different layers of embryonic tissues

What is radial symmetry?

no front and back, or left and right and is restricted mostly to cnidaria

What is bilateral symmetry?

where only one imaginary cut divides the animal into mirror-image halves, appearing in the remaining animal groups

What is cephalization?

concentration of the nervous system and special sensory organs in front of the body and important in directed locomotion

What does cephalization do for animals?

it' is considered an adaptation for locomotion and predation:

• animals can take in sensory information of the surrounding environment

• animals can better detect/capture prey and avoid predators

What is segmentation?

the organization of the body into repeated units along the anterior-posterior axis; repeated units are modified depending on body location

What are three animal phyla known for having segmentation?

arthropods, annelids, and chordates

How does an embryo start developing?

after a sperm (n) fertilizes an egg (n), zygote (2n) undergoes rapid cell division aka. cleavage

What is a protostome?

they cleavage spirally and are determinate

What is a deuterostome?

they cleavage radially and are indeterminate

What are three germ layers that give rise to tissues and organs of animal embryos?

ectoderm

endoderm

mesoderm

What do sponges (Porifera) lack?

they lack true tissues

What characteristics and phylums are diploblastic?

animals that have an ectoderm and endoderm

includes cnidarians (e.g. jellyfish) and a few other groups

What characteristics and phylums are triploblastic?

animals also have an intervening mesoderm layer;

this includes all bilaterians, flatworms, arthropods, vertebrates, and others

What is the mesoderm?

in-between the endoderm and ectoderm — develops into muscles and connective tissue

What differentiates protostomes from deuterostomes?

the blastopore becomes the mouth

What differentiates deuterostomes from protostomes?

the blastopore becomes the anus

What is a coelom?

a fluid-filled body cavity that cushions the internal organs

What did the common ancestor resemble?

modern choanoflagellates

What are choanoflagellates?

single-celled, aquatic microorganism, distinguished by a collar of microvilli surrounding a single flagellum and are solitary or colonial

How did animals differ from choanoflagellates?

they have persistent multicellularity

What did animals (metazoa) evolve from?

unicellular, filter-feeding ancestors

What evolution enabled coordinated body plans, tissues, and movement?

evolution of multicellularity

What are traits of Porifera?

they lack true tissue and organs

sedentary and live in water

suspension feeders

What are three innovations behind animal multicellularity?

Cell adhesion & communication genes (cells can connect and coordinate)

Developmental control networks (allowed patterned growth, differentiation, and body plan formation)

and expansion of extracellular matrix (provided structural support, scaffolding and modes of tissue organization)

What is the anatomy of Porifera?

• choanocytes - flagella circulates water and capture food

• amoebocytes - transport nutrients and produce skeletal fibers (spicules)

• porocytes - span body wall to make pores

• osculum - opening for water

What do eumetazoa possess?

true tissue formed by permanently associated, specialized cells organized into distinct layers

What did the evolution of true tissue enable?

nervous and muscular systems

What are traits of Ctenophora and cnidaria?

they are radially symmetrical and diploblastic

What did bilaterians evolve to have?

a distinct anterior-posterial axis

bilateral symmetry

through-gut

What are three major clades of bilaterians?

ecysozoa

lophotrochozoa

deuterostomia

What are deuterostomes defined by?

an embryonic second-mouth pattern: during development, the blastopore becomes the anus rather than the mouth

What phyla fall into deuterostomia?

chordata, echinodermata, and hemichordata

What are ecdysozoans?

invertebrates that shed their exoskeletons through a process called ecdysis

What traits do ecdysozoans have?

they are protostomes

have a hard exoskeleton (chitin)

segmented body with jointed appendages

What phyla fall under ecdysozoa?

phyla arthropoda and nematoda

What are lophotrochozoans?

they are characterized by a feeding structure called a lophophore, which is a specialized, fan-like feeding organ

some have distinct developmental stage called trochophore larva

What phyla fall under lophotrochozoa?

Mollusca and annelida

Three body cavities are?

Acoelmate, psuedocoelmate, coelems