Body Plans Flashcards
What are metazoans?
Animals whose bodies are composed of cells differentiated into tissues and organs, usually a digestive cavity lined with specialised cells.
What is an opisthokont? Give an example of an opisthokont.
An animal which, if has a flagellum, it is posterior, like a sperm.
An example is a choanoflagellate.
Describe the most important feature of a choanoflagellate
A collar of actin filled microvilli surrounding the flagellum.
How do sponges feed? How does this structure work?
They filter feed using choanocyte cells. These cells have a flagellum surrounded by a collar of microvilli. These are used to create water currents and capture food particles.
In sponges, what type of cleavage occurs in the embryos? What type of symmetry occurs in the adult form?
Radial cleavage in the embryo (zygote divides in even pattern).
There is usually no symmetry- asymmetrical.
Describe the function of these cells present in sponges:
- Porocytes
- Choanocytes
- Archaeocytes
- Spicule
- Pinacocyte
- Porocytes- tubular cells making up the pores
- Choanocytes- filter feeding cells with flagella and microvilli
- Archaeocytes-the foundation of cellular differentiation in all sponge cells.
- Spicule-provide structural support
- Pinacocyte-flattened cells containing many granules; capable of contracting to alter the dimensions of the sponge.
How to ctenophores (comb jellies) feed?
Feeding tentacles covered with cells that discharge sticky material when contacted by prey. Tentacle retracted to mouth when food captured. In some species entire body is covered with sticky mucus.
Name a cellular structure in cnidarians which allows them to be predators.
Cnidocyte cells which contain organelles called nematocysts (cnidocysts) which can inject toxins into prey.
Describe a cnidarian lifecycle.
The sessile asexual polyp alternates with the medusa jellyfish like form.
How do corals flourish in nutrient poor waters?
Endosymbiotic relationships with unicellular photosynthetic protists which live inside the cells in th polyp
How are hard corals formed?
They secrete an organic matrix on which calcium carbonate is deposited.
What is coral bleaching and what causes it?
Coral death and loss of colour due to a change in temperature, causing the zooxanthellae (unicellular photosynthetic protists) to be expelled.
What re diploblasts and triploblasts and what kinds of tissues of they form?
Diploblasts have two germ layers- the endoderm and ectoderm.
Triploblasts have three germ laters- the endoderm, mesoderm and ectoderm
What type of symmetry do diploblasts and triploblasts exhibit?
Diploblasts: radial symmetry
Triploblasts: bilateral symmetry
What is the process called by which the three (or two) germ layers are formed?
Gastrulation
What characterises protostomes and deuterosomes?
Protosomes- In the blastula stage, the embryonic blastopore becomes the mouth.
Deuterosomes- * In the blastula stage, the embryonic blastopore becomes the anus
What type of embryonic cleavage occurs in protostomes and deuterosomes?
Protostomes- spiral cleavage
Deuterosomes- radial cleavage
What’s the difference between coelomate, acoelomate and psuedocoelomate
Coelomate- has fluid filled body cavity surrounded by a muscle layer covering the organs plus an outside muscle layer
Acoelomate- no fluid filled body cavity
Psuedocoelomate- have a fluid filled space in which internal organs are suspended. This is enclosed by muscles on the outside but not on the inside
What is a hydrostatic skeleton?
The system of support found in soft bodied invertebrates which relies on the incompressibility of the fluids in the body cavity which provides support for the internal organs
Give examples of platyhelminthes. Are they coelomate? How does their gut system work?
Flat worms, flukes and tapeworms.
Are acoelomate.
Their mouth leads to a ‘blind end’ but they have highly branched guts which leads to a large surface area for absorption. (pharyngeal opening serves as both mouth and anus.)
What are flame cells and what do they do?
Specialised semipermeable cells which provide basic ultrafiltration, like a kidney. Allows flow down excretory canals due to cilia.
How do rotifera feed?
Have a corona of cillia around the mouth which draws a vortex of water into the mouth . Method of filter feeding.
Describe what is meant by metametic segmentation in true worms (annelida).
The repetition of organs and tissues at intervals along the body of an animal, thus dividing the body into a linear series of similar parts or segments (metameres).
What are the three main components of the body plans of molluscs? Describe these features.
- Muscular foot- flat structure used for crawling
- Visceral mass- the soft, nonmuscular metabolic region of the mollusc. It contains the body organs.
- Mantle- covers the visceral mass and secretes the calcareous shell
