Introduction to Animalia - Trip/dip/loblastic, coelom, metameric segmentation etc.

Characteristics of Kingdom Animalia

• motile → in search of food, mate or escape predation

  • or can only move certain body parts or only in larval stage

• multicellular

• eukaryotic

• no cell wall chloroplasts and permanent central vacuoles

• perceive env through receptors connected to nervous system

  • nervous system and support system evolved tg

• sexual reproduction

• holozoic heterotrophs

• have a blastula

Explain how development of cephalization is linked to being motile

1. motile organisms had to develop complex sensory organs to perceive and navigate their environment

2. conc of sensory organs was developed at the front of organism → first body part to encounter hostile situation

3. concentration of complex sensory organs needed more sensory processing system

4. lead to nerve swellings - ganglia

5. lead to cephalization

Blastula Stage

• early developmental stage

• when zygote divides forming a hollow layer of cells → BLASTULA

  —-

• entire cell is called a blastula,

• the actual fluid filled cavity is the blastocoel,

• cells making up blastula are blastomeres

• the outer spherical layer of blastomeres is the blastoderm

Define Radial Symmetry

• organism can be divide into two equal halves across any plane passing through the axis in the center

Evolution of Radial Symmetry

• early animals were sessile/didn’t move much

• radial symmetry allowed for all around awareness to capture food and detect potential danger

Define Bilateral Symmetry

• organism has similar anatomical parts arranged on opposite sides of a median axis so that only one plane can divide it into essentially two identical halves

Evolution of Bilateral Symmetry

• as animals became more motile - concentration of sensory organs to the front (front end perceives danger first)

• animals developed anterior, posterior and two laterals → BILATERAL SYMMETRY

• cephalization

Advantages/Disadvantages of Radial/Bilateral Symmetry

• co-ordinate sides for locomotion

• two eyes allows for better vision estimate distances

• specialization of body parts

• no all around awareness

• injury to the head can be fatal

---

• all around awareness

• less advanced nervous system due to no cephalization

• limited movement efficiency

Distinguish between radial and bilateral symmetry

• Radial

  • sessile organisms like cnidaria

  • all around awareness

  • definition - two equal halves on any plane

• Bilateral

  • motile organisms

  • one plane of symmetry

  • cephalization

  • localization of sensory organs

  • evolution of paired appendages

  • facilitates stream-lining like arthropoda

Diploblastic organisms

have 2 germ layers

• ectoderm - nervous tissue, epidermis and nephridia if present

• endoderm - develop into gut and associated glands

• have a mesoglea - layer of non cellular gelatinous layer

Triploblastic Organisms

3 germ layers - Gastrula

• ecto/endoderm

MESODERM- the 3rd germ layer

• muscles

• dura mater

• bones

• cartilage

• connective tissue

• endothelium of blood vessels and blood cells

• dentine of teeth

• kidneys

• adrenal cortex

Evolutionary Significance of Triploblastic organsisation

• 3 germ layers: ectoderm, mesoderm, endoderm

• Mesoderm allows muscles & internal organs

• Enables complex body structures

• Supports larger size & active movement

• Foundation for coelom and organ systems

Coelom

• mesoderm splits into two layer

  • one lining ectoderm, one endoderm

  • surrounded by peritoneum

• the fluid filled cavity between these layers is called the coelom

Advantages of a Coelomic Cavity

• more space for internal organs → larger and more complex

• space where organs can grow and develop

• movement no longer hampers digestion

• more space for the uterus to expand

• hydrostatic skeleton

• more space for food or waste

Metameric Segmentation

• serial repetition of organs or tissues along the body of an animal dividing body into similar parts or segments (Metamers)

Metameric Segmentation allows for locomotion

• repeated segments of annelid are easy to coordinate

• Segments contract in a wave (circular then longitudinal muscle).

• This creates efficient, coordinated movement,

Metameric Segmentation also allows for the specialization of body parts

• different segments can be adapted to do different things

Tagmata

metamers became grouped - further specialization each tagma can develop unique structures

Examples of Metameric Segmentation in Humans

• vertebral column

• intestinal wall

• division of nerve endings

TABLE SUMMARIZING ANIMAL PHYLA PG 15