Within a marine ecosystem all the organisms can be classified into different
taxonomic groups based on their body systems and physical characteristics
The body systems of organisms tell us about how an animal gets its energy
How does it get its oxygen how it responds to the environment? And how does it reproduce?
Animals are placed in taxonomic groups based on similar characteristics of the body
however, sometimes we have to look very closely at animal body systems and features to make a classification a
Shark and an orca might look similar, but one is a fish and one is a mammal and they have quite different body systems
We classify living organisms into groups starting from those with broad
similarities up to organisms with very similar body features
this movie clip will focus on some of the common marine phylum groups of the animal kingdom the
Phylum Porifera is made up of sponges
porifera means having pores or little holes
Sponges are one of the least complex groups of animals, but even though they don't have a brain eyes or a heart
They are still animals because they are heterotrophs
Meaning they can't make food from photosynthesis like autotrophic plants or algae
These deepwater sponges are filter feeding that is sifting plankton and nutrients through their pores
They also get all the oxygen they need directly from the water
Sponges have a skeleton that is made of calcium or silica and this supports their body tissues
the phylum Cnidaria contains jellyfish sea anemones and corals
These animals all have stinging cells called nematocysts
The word Cnidaria comes from the Greek word for sea nettle
Jellyfish have soft bodies with very basic body systems minimal eyes. No brain. No gills or a heart
They tend to drift with the current
A nematocyst is a capsule that contains a barb that injects venom into the victim causing a painful and
Sometimes even fatal sting
Some jellyfish can still sting even if they are washed up on the beach because then Anematocyst can still be active
Anemones are kind of like an upside-down jellyfish
Their body is stuck to the rock and their tentacles extend upwards which they use to catch prey
Comb jellies or ctenophores may look like jellyfish, but they don't possess stinging cells. So they are classified in a completely different phylum
The phylum echinodermata
Contains a group of marine animals with rough or spiky skin
Sea stars sea urchins and sea cucumbers are echinoderms
Sea urchins are radially symmetrical animals that are covered in spines which are used for defense and movement
The mouth is on the underside or ventral side of their body
as
Well as spines, urchins also have tube feet which are operated by a water vascular system that pumps water
around the body
Sea stars also have hydraulically powered tube feet that they use for locomotion and opening up shells to feed on
Their mouth is also on the underside of their body
sea stars utilize
External digestion where the stomach is everted out of the animal's mouth and digestive enzymes are released onto the prey
Usually while it is still alive
Sea stars have chromatophores which are colour pigment cells the colour of cushion stars can vary greatly
They also have a remarkable ability to regenerate body parts
Sea stars have no eyes, but they can detect light from the tips of their rays
Molluscs are a diverse group of animals. They have a soft body with no skeleton
Some have shells and some have only a residual shell or no shell at all like this intertidal slug
Bivalve molluscs have a shell that is hinged in it two halves
mussels oysters
And scallops are bivalves some have eyes like this scallop and some have no eyes
Sea snails that have only one shell are called gastropods
They can be carnivorous
Like this tulip shell and the whelk
Or they can also be herbivorous grazing on algae like this periwinkle
Octopus squid cuttlefish and Nautilus are also molluscs from the class cephalopoda an
Octopus is in the phylum Mollusca
because even though it no longer has a shell it has a body structure called a mantle the shell of bivalves and
Gastropods is made by the mantle
octopus also have colour pigment cells called chromatophores
However, unlike echinoderms octopus can change their color very rapidly
They can also change the texture of their skin
The phylum Arthropoda
Contains animals that have jointed legs and a segmented body
Crustaceans are a subgroup of the arthropod phylum the decorator crab covers itself in seaweed for camouflage
The Velvet crab is a fast swimmer with its back legs adapted as paddles
This hairy crab is a female and carries her eggs on her abdomen
Crustaceans such as this southern rock lobster have an exoskeleton made of chitin which is a kind of protein
The exoskeleton has to be molded which is dangerous for the animal until the new exoskeleton
becomes hard and provides protection again
Many crustaceans have antenna and antennules as part of their sensory system
These are used to sense chemical particles in the water to help with locating food
Barnacles might look like a mollusc on the outside, but they are actually an arthropod
They have jointed legs that they use to catch food by extending their legs out through the hard outer casing
The phylum Chordata
contains animals with the most complex body systems
The animals that we have seen previously are all called invertebrates meaning that they do not have an internal skeleton with a backbone
Animals in the chordate group have a nerve cord at some stage during their lifecycle
This phylum is divided into the vertebrate animals that we are familiar with but also sea squirts
The subphylum vertebra contains animals with a backbone with vertebrae protecting the spinal cord
the spinal cord being a very important part of the complex central nervous system of vertebrates the
subphylum to Tunicata contains tunicates or sea squirts
These animals often look very simple from the outside
They used to have a notochord which is a less complex form of spinal cord when they were a larval stage
Here we can see the larval stage of a tunicate under a microscope
when it develops into an adult, it will lose the tail and the ability to swim and
Become a sessile animal stuck to a rock or other hard substrate
It is still more closely related to humans than sponges
Marine examples of vertebrates are bony fish such as this scorpion fish seahorse
And flathead
They have gills to extract oxygen out of the water and may be herbivorous omnivorous and carnivorous
Cartilaginous fish are sharks skates and rays
These animals have a skeleton made from cartilage which makes them very flexible in the water
Some lay eggs, and some have live babies
See mammals like whales dolphins and seals have lungs to breathe air
Dolphins and whales have a blowhole which is a modified nostril
Mammals, give birth to live young and feed their babies milk
Seals and sea lions are adapted to be able to spend time on land as well as water
They don't have a blowhole but nostrils at the end of their snout
Sea birds, like oyster catchers live near the coast eating small invertebrates
Herons are waders that catch fish
Birds like albatross feed in the open ocean and a strong fliers
Marine reptiles are usually rare in Tasmania
Although the increasing warm waters of the East Australian current may be bringing marine reptiles to Tasmania from northern, Australia
In summary
Classification and taxonomy is a system of arranging living organisms into different groups based on similar body features

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