bio 2 animals diversity

General Features of Animals

Heterotrophy ( energy and orgnaic molecules by ingesting other organisms)

Multi cellualrity ( many compelx bodeis)

Unique cell junctions ( anchoring, tight, and gap junctions)

Active movement ( rapid and complex)

Diversity of form ( small as unaided eye or enermous)

Not autrtohpic or photosyntehtoc ( opnhistka group)

Movement

most muscles has nerve cells organized into tissues

Muscle tissue is unique to animals

most capable of locomtoion while some are sessile ( no movement)

specialzed sesnroy strucutres and a nervous system to coordiante movement

sessile speices ( barnacles) have moving appaendages or swimming larval stage

Modes of nutrition

Suspension feeding ( filetirng particels from surronding water)

Bulk feeding ( eating large food pieces)

Fluid Feeding ( sucking sap or animal body fluids)

INTERNAL ABSORPTIVE nutrition

Additonal general features

Diversity of habitat, most in sea, but many are in freshwater or land

Sexual reprodction ( most reproduce sexually, animal eggs ( nonmobile)

Embryonic development ( zyogte first undergoes series of mitotic divisions that produce ball of cell)

Tissues ( cells of most animals are orgaizned intro sturcutral and functunctional units called tissues)

Reproduction and Development

Nearly all animals reproduce sexually,

Small, mobile sperm unite with a large egg to produce a zygote

Internal fertilization is common in terrestrial species

External fertilization is common in aquatic species

Metamorphosis (a developmental phenomenon in which juveniles change into adults, reduces competition within their own species, and facilitates dispersal)

Evolution of the Animal Body Plan

symmetry, tissues, body cavity, patterns of embryonic development, segmentation

Symmetry

evolution of symmetry

(started with spognes, which lack any definite symmetry)

(All other animals have symmetry defined along an imaginary axis through the animal's body)

(the other two types of symmetry: radial and bilateral)

Types of symmetry

Asymmetrical

( does not have any line of symmetry) ( EX: sponges)

Eumetazoa ( divided by symmetry)

Radial Symmetry ( radial exemplifies this)

( body parts arranged around the central axis)

( It can be divided into two halves by any plane that passes through the center)

Bilateral symmetry

(The body has right and left halves that are mirror images)

( only the sagittal plane is divided into two halves that are mirror images)

Advantages of bilateral symmetry

Cephalization

( evolution of a definite brain area)

( directional movement)

Tissues

zygote ( fertlized eggs are totipotent, they can give rise to all other cells)

As the embryo develops, the cells specialize

irreversible process except in sponges

( sponges do not have defined tissues and organs)

( ability to disaggregate and aggregate their cell)

Evolution of Body cavity: germ layers

Sponges lack germ layers

Cnidarians are diploblastic: Endoderm and Ectoderm

Most animals have embryos that produce 3 germ layers ( triploblastic)

Outer ectoderm: body coverings and nervous system

Middle Mesoderm: Skeleton and muscles

Inner Endoderm: Digestive organs and intestines

All triploblastic animals have bilateral symmetry except adult echinoderms

also called cell layers that arise in gastrualtion

Germ layer examples

Radiata: two layers diploblastic, form endoderm ( digestive tract lining) and ectoderm ( rise to skin and nervous system),

Radiata do not form mesoderm due to the fact they have no organs

Bilateria: have ectoderm and endoderm but also mesoderm ( gave rise to msucles and most internal organs ( skeletal as well))

Body cavity

Sponges lack germ layers

Cnidarians are diploblastic: Endoderm and Ectoderm

Most animals have embryos that produce 3 germ layers ( triploblastic)

Outer ectoderm: body coverings and nervous system

Middle Mesoderm: Skeleton and muscles

Inner Endoderm: Digestive organs and intestines

All triploblastic animals have bilateral symmetry except adult echinoderms

also called cell layers that arise in gastrualtion

Functions of the Coelom

cushions internal organs

enables the movement and growth of internal organs independent of the body wall

functions as a hydrostatic skeleton ( muscle contractions push fluid from one part of the body to another, fluid acts as a simple circulatory system)

Circulatory systems

Coelomates developed a circulatory system to flow nutrients and remove wastes.

Open circulatory system: blood passes from vessels into sinuses, mixed with body fluids, and reenters vessels

Closed circulatory system. Blood moves continuously through vessels that are separated by body fluids

Different patterns of development

Basic bilateral pattern of development

Mitotic cell divisions ( cleavage) of the egg form a hollow ball of cells ( blastula)

blastula then indents to form a two-layer thick ball that has a blastopore ( opening to outside), Archenteron ( primitive body cavity)

Groups of bilaterians

Protostomes

develop the mouth first from or near the blastopore

(anus, if present, develops either from the blastopore or another region of the embryo)

Deuterostomes develop the anus first from the blastopore

(The mouth develops later from another region of the embryo)

Differences between Protostomes and Deuterostomes

1. Cleavage patterns of embryonic cells

Protostomes = spiral cleavage ( new cells from right to left of previous cells)

Deuterostomes = radial cleavage ( new cells form on top of previous cells)

2. Developmental fate of cells

Protostomes = determinate development (cell fate determined early)

Deuterostomes = indeterminate development ( cell fate not determined until after several divisions)

3. Formation of the Coelom

Protostomes = cells move apart to form coelom

Deuterostomes = groups of cells pouch off to form coelom

Segmentation

Segmentation provided three advantages.

1. allows redundant organ systems in adults, such as occurs in annelids

2. allows for more efficient and flexible movement because each segment moves independently

3. allows specialization of body regions

Annelids, arthropods, and chordates exhibit segmentation, first appearing in Annelids

History of animal life

First animals Invertebrates

Increase in animal diversity in the Cambrian explosion

3 explanations

1. favorable environment ( warm temp, increase of atmospheric and aquatic oxygen, development of ozone layer

2. Evolution of the Hox gene complex ( variation of morphology)

3. Evolutionary arms race

Animal Phylogeny

Previously, Anatomy and embryology have been used to infer phylogeny

past 30 years, sequence data have accumulated ( may suggest different phylogenetic relationships)

Currently, we have molecular data which we construct new phylogenies from

Choanoflagellate-like- ancestor

Choanoflagellates are the closest living relatives of animals

They are single-celled protists with a single flagellum surrounded by a collar of cytoplasmic tentacles

Some are colonial

Some cells have specialized functions

Some are similar to sponge chaoncytes

Classification of animals

Sponges are monophyletic

Eumetazoa is all animals other than sponges and consists of Cnidaria and Bilateria

Cnidaria branch off the evolutionary tree before Bilateria

Development in Animal Phylogeny

Annelids and arthropods were separated into different clades, thought to be closely related

Arthropods are grouped with the Ecdysozoans

They undergo ecdysis ( molting)

Molt their cuticles

Protostomes divisions

Two groups

Lophotrochozoans

Grow by gradual addition to body mass (metamorphosis?)

Ecdysozoans

Animals that molt

Includes the arthropods and many other phyla

Deuterostome Divisions

Two groups

Chordates

Echinoderms

Fewer phyla and species than protostomes

Parazoa

Only one phylum: Porifera

"pore beares"

ony sponges

loosely organized and lacks true tissues

multicellualr

assymetircal

mostly marine

Adults are sessile, larvae are free swimming

Sponge Functional Layers of the Body Wall

1. Outer epithelium

made up of flattened cells

watet comes in ostia, comes out through osculum

2. Mesohyl

middle layer - gelantionus matrix

spicules - needles of calcium carbonate

spongin - reinforcing tough protein fibers

3. lining of the internal cavity ( choanocytes)

Collar cells

Flagellated - contributes to water circulation

face internal cavity

Engluf and digest food from passing water

Sponge reproduction

Asexual

(Fragmentation)

Sexual

Choanocytes transform into sperm

sperm captured and passed to the egg cell in the mesohyl

development may occur within the mother or in open water

larva is planktonic; will settle and transform into an adult

Eumetazoa

Animals with true tissues

Embyros with the distinct layers (endoderm, mesoderm, and ectoderm)

True body symmetry ( radial and bilateral)

Radiata ( radial symmetry)

Phylum Cnidaria

( Jellyfish, box jellies, hydra, sea anemones, corals)

Phylum Ctenophora

(comb jellies)

Combined: only two embryonic germ layers ( no mesoderm)

Gelatinous mesoglea connects layers

Phylum Ctenophora

Comb jellies,

8 rows of comblike plates of fused cilia that beat in coordinated fashion (bioluminescence)

2 tentacles covered with colloblasts discharge a strong adhesive used to capture prey

Phylum Cnidaria

Diploblastic

distinct tissues but no organs ( no reproductive, circulatory, or excretory systems)

No concentrated nervous system

(latticework of nerve cells,)

(touch, gravity, light receptors)

Capture Orey with nematocysts

( unique to this phylum)

Cnidaria body forms

Polyps - cylindrical and sessile ( many build a chitin or calcium exoskeleton), some even build an internal skeleton

Medusa - umbrella-shaped and free-living

commonalities

single opening leading to gastrovascular cavity ( site of digestion, most gas exchange, waste discharge, and formation of gametes in many)

the cavity serves as a hydrostatic skeleton, gives shape, and provides structure where muscles can operate

Two layers to the body wall,

epidermis

gastrodermis

Mesoglea occurs between layers

Cnidarian Life Cycle

Many alternate between polyps and medusae

Both phases consist of diploid individuals

In general, species with both phases, the medusa forms gametes

( sexes separate)

(Gonochorism - individual is either male or female)

( zygote develops into planktonic planula)

(metamorphosis into polyp)

(polyp produces medusae or other polyps asexually)

Cnidarian digestion

evolutionary innovation of the extracellular digestion of food inside the animal

Digestion takes place partly in the gastrovascular cavity

Cells that engulf fragments by phagocytosis

Nematocysts

Cnidarians use these nematocysts to capture prey

secreted within the nematocyte

The mechanism of this discharge is unknown

Some can carry venom

The 5 cnidarain classes

Anthozoa ( sea anemones, most corals, sea fans)

Cubozoa ( box jellies)

Hydrozoa (hydroids, hydra, Portuguese man-of-war)

Scyphozoa ( jellyfish)

Saturozoa ( star jellies)

Bilaterian Acelomaates

Characterized by bilateral symmetry

allowed for high levels of specialization

divided into two clades

protsomes and Dueterostomes

Acoel flatworms

Phylum Acoela

Acoel flatworms were once considered basal members of the phylum Platyhelminthes

have a primitive nervous system and lack a digestive cavity

Based on molecular evidence, simialrites are convergents