Lecture 25 Flashcards Preview

Genetics > Lecture 25 > Flashcards

Flashcards in Lecture 25 Deck (30):

How many living animal species are described? What percentage do the insects, molluscs, ctŕustaceans, mammals and primates make up?

1.7-2 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?


-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?


-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


-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


-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?

1. symmetry- what kind?

2. germ layers- how many?

3. coelom (body cavity)- present or absent?

4.blastopore- does it form anus or mouth?

5. segmentation- present or absent?


What are the 2 types of symmetry?

1. bilateral= -have one plane along which they are symmetrical

-can talk about anterior/posterior, dorsal/ ventral, left/right


2. 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?


-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?

1.moulting (Edysozoa-arthropods)

2. feeding mechanisms

3.larval biology



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?

1. Hydras (Hydrozoa)

2.Jellyfish (Scyphozoa)

3.Corals and anemones (Anthozoa)


What are the characteristics of the phylum cnidaria?

-radial symmetry (mostly)




-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


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?


--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


           What are the characteristics of the class Hydrozoa?


-freshwater polyp

-long tentacles for prey capture-with stinging cells

-anchored by "foot"

-spent lot of the time=as a polyp


What are the characteristics of the class Schyphozoa?


-marine, free-swimming

-also have stinging tentacles (sometimes very poisonous)

-one of the world's longets animals (200ft) long is the lion's mane jellyfish

(80m tentacle sin lion's mane jellyfish)


What are the characteristics of the class Anthozoa?

-anemones and corals

-marine polyps

-often colonial

-many have symbiotic algae living intra-cellularly

(coral provide algae with nutrients and protection)

(-algae provides coral with N2 and organic C compounds)

--algae provide coral with nutrients etc

if the larvae aren't there= coral goes white and dies
-radially symmetric, diploblast simple nerve mats


What are the characteristics of the phylum Platyhelminthes?


-two modes of living: free-living aquatic or parasitic

-four classes

-bilateral symmetry



-protostome (simple gut with mouth only)


-bottom surface covered in cillia= aids movement

-separation of anterior and posterior end= there is mass of nerve cells in the head


What are the four classes of Platyheminthes?

Turbellaria: aquatic free-living flatworm, colourful

Monogenea:extrenal flukes, parasitic

Trematoda: internal flukes, parasitic

Cestoda: tapeworm, parasitic



What are the characteristics of tapeworms? (class Cestoda)

-vertrebrate gut parasites

-famously used as diet aid

-attach to intestinal lining via head structure (scolex)

-feed by absorption through epidermis

-reproduce by breaking off body segments (proglotttids)

-can grow very long

is very thin= can feed trhough absorption
they grow in segments= each bit is segment of egg and sperm= can become new tapeworm= it  is not segmented as such as it is not fixed in the adult individual