Lecture 25 Flashcards
How many living animal species are described? What percentage do the insects, molluscs, ctŕustaceans, mammals and primates make up?
- 7-2 million living animal species desribed
- 75% insects
- 6% molluscs
3% crustaceans
- 0.4% mammals
- 0.02% primates
How many species are possibly in the world?
-numbers of species estimated up to 10 million living but only up to 2 million described
Into how many phyla is the animals kingdom described?
30+
- phylum is the highest unit of calssification after Kingdom
- animals are grouped into phyla based on shared characteristics
What does it mean that animals are heterotrophs?
animals= heterotrophs, need to consume other organisms to survive, don’t have cell walls
What were one of the earliest animals?
- sponges
- on the left
What are the characteristsics of the phylum Nematoda?
- round worms
- many species (c 25 000 described)
- aquatic and terrestrial
- important parasites (all plants and animals) have at least one nematode
- most abundant animals in Antarctica
- moult (like athropods)
- eutelic (fixed number of cells/species)
What are the characteristics of the phylum Onychophora?
- velvet warms or claw bearers
- terrestrial
- have antennae (unique for worms)
- capture prey by throwing out sticky threads (like a web)
What are the characteristics of the phylum Bryozoa?
- encrusting aquatic organisms
- colonial
- feed with modified foot (lopophore)
What are the characteristics of the phylum Tardigrada?
- “water bears or moss piglets”
- live in fresh water, moss and undergrowth
- capable of surviving extremes (10 years without water)
- on final flight of space shuttle Endeavour
- also eutelic (specific number of cells)
What are the 5 criteria to help classify phyla?
- symmetry- what kind?
- germ layers- how many?
- coelom (body cavity)- present or absent?
- blastopore- does it form anus or mouth?
- segmentation- present or absent?
What are the 2 types of symmetry?
- bilateral= -have one plane along which they are symmetrical
- can talk about anterior/posterior, dorsal/ ventral, left/right - radial symmetry= have several planes along which they are symmetrical
- bilateral= most common= us
What are the germ layers?
-layers of embryo cells that develop into body features
two layers= diploblastic
three layers= triploblastic (have the mesoderm= capable of differentiating into many tissues and features)
What is the blastula?
-early developmental stage when cells begin to differentiate
fertilisation- morula-blastula then the three layers= as bent get the future gut, opening to it= blastopore
=simplest organisms pretty much that, no more differentiation
What is the coelom, who has it and why is it important?
- triploblasts
- coelom present= coelomate
- coelom absent= acoelomate
importance: fluid filled so can be used for internal support - separates internal processes from gut
- allows transport of fluids (circulatory and excretory systems)
- provides space for development of internal organs
- enables body size
- allows increase in girth
What does the blastopore become?
PROTOSTOME: mouth first, either blastopore becomes mouth, anus later or blastopore becomes mouth and anus at the same time
DEUTEROSTOME: blastopore becomes anus, mouth develops later
What is segmentation?
- is the body divided into segments?
- segmentation affects the mesoderm and ectoderm
What are 4 other ways of distinguishing animals?
- moulting (Edysozoa-arthropods)
- feeding mechanisms
- larval biology
- reproduction
Which phyla do we study?
What are the characteristics of the phylum Porifera (sponges)?
- simplest animals
- aquatic, mainly marine
- no mouth or gut
- layers of cells with protein matrix, no tissues or organs
- no nervous system
- mainly filter feeders
- have specialised cells= pinocytes= can engulf larger prey
- sexual and asexual reproduction
- two layers of cells
minimal means of responding to the outer environment
can release sperm and eggs out into the environment,
-symmetry, radial nor bilateral
What are the three classes into which the phylum Cnidaria is divided into?
- Hydras (Hydrozoa)
- Jellyfish (Scyphozoa)
- Corals and anemones (Anthozoa)
What are the characteristics of the phylum cnidaria?
- radial symmetry (mostly)
- diploblastic
- acoelomate
- unsegmented
- nerve net
- reproduction= usually sexual
- two germ layers
- simple but step up from sponges
- nerve net on the outside
-=nervous system sort of
-no posterior and anterior part
-can tell different between light and dark
-it is in the mesoglea
photoreceptors
What is the body structure of a cnidarian?
- two body layers are separated by a gelatinous layer= mesoglea
- polyp form= just sits there
most have a second form= medusa= moving swimming form
if you take polyp turn upside down= medusa almost= very similar some of the names for things change
What do cnidarians use to catch prey?
-nematocysts
–use cell nematocyst to sting and catch prey
-it is in the cnidocyte
there is a trigger= move there= shoots it out-transfers poison or toxin= hurts
Describe the cnidarian life cycle:
planula=larvae= swims around
-time spent in each depends on the species, jellyfish= sexual, coral= polyp asexual most of the time
