week 6 Flashcards
What are Invertrebrate metazoa?
Metazoa-Multi-cellular animals.
Invertebrates- Animals without backbones.
Invertebrate Metazoa- Sometimes described as non-chordate metazoans.
What are some example of invertebrate metazoa?
Porifera - sponges Cnidaria Platyhelminthes - flatworms Nematodes - roundworms Annelids - segmented worms
What do molecular evidence also support?
Molecular evidence also supports this idea that choanoflagellates are basal to the metazoans or at the base of the metazoan phylogeny.
So metazoan phylogeny, i.e. DNA sequencing construction is an active area of research.
How did the invertebrate metazoa evolve?
Graph shows a comparison of genes that are shared between different organisms So the numbers in the brackets underneath that particular groupings are the number of genes used and while the worm considered here C elegans worm in the centre of the slide this has 19,000 genes and humans had around 35,000. So this comparison only used a subset of the number of genes in a human. Percentages show the number of genes that are shared between these groups. Sharing a lot of genetic material through the tree of life.
Where do the Porifera (sponges) fit?
Phylogeny represents a hypothesised evolution of these changes to our body plan. It is suggested that the ctenophores branched off before the Porifera or the sponges, suggesting that as sponges have this very simple body organisation this phylogeny would suggest that this simple sponge body is an evolutionary deprived state rather than evolution it ancestral state. Derived state has come about through evolution. Ancestral state as one that you inherited from your ancestor. Implying that sponges have become simplified over time rather than having a simple ancestor or ancestor with a simple body form. All phylogeny reconstructions as we weren’t around to witness how animal life involved therefore most are different.
why is there great diversity of metazoan?
Great diversity of metazoan forms because of the competition for resources organisms have evolved to exploit all sorts of ecological niche is to survive and keep ahead of the competition sponges have exploited a pretty unique niche within the metazoans whereby instead of moving through their environment like other metazoans they actively pump their environment through themselves.
Sedentary they don’t move around
Share a very simple level of organisation among the Metazoa with just four cell types in an absence of true tissue layers.
Higher numbers in marine environments may suggest that they have more floating food particles in them so this filter feeding lifestyle just is better suited to marine habitats.
What are Recognition systems the basis of?
Recognition systems are the basis of an immune system and allows the recognition of different individuals of the same species as well as recognising pathogens.
What does the pattern of branching describe?
the pattern of branching describes the relationships between groups
Metazoa =
Invertebrate Metazoa =
Metazoa = animals Invertebrate Metazoa = animals without backbones
Hypothesised origins from
colonial choanoflagellates
Several advantages to being
multicellular
Fossil evidence
poor for origins
Metazoans most likely evolved
~700, 1500 mya
What is widely accepted when it comes to the Choanocytes?
It’s widely accepted that these are the ancestors of the metazoans in both you can see the kind of apical collar and sensual flagellum and there’s somebody at the bottom
What are some properties of Choanocytes?
These choanocytes are flagellated with an apical collar and line the sponge atrium making up these Choanoderm layers.
—Choanocytes have a flagellum also has its flagellum vein which adds surface area to the structure and then we have this apical collar which is made up of multiple microvilli. What happens is the flagellum beats a move side to side forcing water out of the apical collars top. As his apical collar beats and forces water out through the top of the apical colour that also is water in through this Apical collar through these parallel microvilli. As this happens food gets caught in the apical collar and the mucus helps collect these food particles. So the sponge is a filter feeder and the particles from which the feet can be prokaryotic or eukaryotic cells noncellular disperse organic matter. So these get stuck in the mucus that’s on the apical collars and then this is drawn down towards the cell body. The choanocytes have a really important role in capturing the suspended material from the sponge to feed off by beating this flagellum. Once his food particles make their way down to the main cell body there than phagocytosed which is where the cell envelops the small food particles during them into itself.
How is food transported in choanocytes?
So the food is tracked by the choanocytes but these few particles are then passed on to be to the amoebocyte which is the final site of digestion in sponges so if you just collected the choanocytes passed on to the Amoebocyte for digestion. Waste products are passed out of the sponge by diffusion and released into the environment as such a large volume of the sponge is in direct contact with the water and for respiration this gas exchange is also done by diffusion in a similar way. So there’s this exchange of respiratory gases into the surrounding water. This can only happen because almost all the cells of the sponge within 1 mm or flowing water through the Sponge body.
For animals symmetry is either
radial or bilateral.
Cnidaria - where do they fit in?
Around 10,000 describe species of cnidarians Found in shallow seas where they either attach to hard objects or burn sediment or drift in the plankton layer. There are a few cnidarian Significant to us as humans for instance some species with the genius hydra Are common in laboratory and textbook examples. And worldwide the diversity perhaps reaches its zenith in coral reefs that exceed rainforests in terms of species diversity at an ecosystem level.
What do colonies contain?
Colonies contain individuals with many different body forms specialised for different functions. And in this way some colonial cnidarians can be thought of as having a modular design, being made up of specialised units and reaching considerable complexity. Sometimes these colonies can have thousands of individuals which you see in many coral species before the Portuguese man of war that you can see they’re only for genetically identical individuals zooids here.
What are some properties of polypoids?
Polyploid cnidarians are generally considered to have a mouth up orientation as the oral service is at the top of the individual and these polyploid cnidarians are generally considered sessile, they don’t move through the environment. Some can contract and relax their muscles to get rid of predators.
How do Medusoids generally swim?
Medusoids Generally swim in this pulsating movement with the mouth down orientation as the oral surface is generally downward facing.
What do body arrangements consist of?
Both body arrangements consist of two true tissue layers making the cnidarians diploblastic. Two layers of this epidermis around the outside between these layers we have the mesoglea and the second tissue layer is the gastrodermis surrounding the gastrovascular cavity. Epidermis and Gastrodermis are our true tissue layers. So the cells sit on an extracellular matrix called the basal laminar. And they’re actually connections between the cells called intracellular connections. And these constitute these layers of true tissues. In both body forms epidermis and the gastrodermis are separated by this non-cellular Mesoglea which has this Kelly like appearance. And it contains collagen fibres, it can be defined by muscle action but will revert to its original shape. Who has a structural or skeletal function. Both have an oral surface where the entrance and exit to the gastrovascular cavity is and on the opposite surface aboral surface. The gastrovascular cavity is therefore multifunctional and it’s involved in a number of things such as digestion circulation and absorption as well as acting as a hydrostatic skeleton or brood chamber for a developing young.
Where are myofibrils found in Cnidaria muscles?
Myofibrils occur in the Appear in the epithelial layers. find them in the epidermis and in the gastrodermis. Circular muscles are significant in these umbrella shape Medusoid forms it’s these muscles which are responsible for this pulsation movement which allows the Medusoid cnidarians to move around the environment.
What are some other properties of cnidarians?
We also see nerves in the simplest form and in the cnidarians we have sensory neurons which connect to sensory receiver cells you find around the body of the Cnidarians. Also have motoneurons to control his muscle fibres and these are all connected by the diffuse nerve net. Impulses can travel in any direction through the net. You find nerve rings that go around the oral or aboral axis, are associated with sensory organs such as light detecting structures and also important in innovating these swimming muscles to generate these pulsing motions.
