Lecture 10 Flashcards
What does the life cycle of an animal encompass?
Its embryonic development, birth, growth to maturation, reproduction and death
What is the pattern of development called when newborns are similar to adults in many ways?
Direct development
What is a larva?
An immature life cycle that has a different form to an adult
What is the radical change that butterflies, beetles, bees, moths and flies undergo between larval and adult stages?
Metamorphosis
Give an example of larval and adult stages being specialized for feeding and the other for reproduction/
Adults of most moth species do not eat Butterfly larvae (caterpillars) eat leaves and flowers, adult butterflies eat nectar
Why do animals have different life cycles specialized for feeding and reproduction?
It increases the efficiency with which the animal performs a particular task
What do all life cycles have?
At least one dispersal stage
When do animals that are sessile as adults disperse?
As eggs or larvae- for example, sessile marine animals larva float freely in the plankton
What do animals that live on the sea floor, including polychaete worms and mollusks, have as a common larvae form?
A trochophore
What is the larval form of bilaterally symmetrical marine animals, including crustaceans?
Nauplius
When do animals that are motile as adults disperse>
When they are mature
Give an example of a motile animal dispersing after reaching maturity.
Caterpillar feeds on a single plant- after metamorphosis it may fly and lay eggs on far away plants
What is a trade-off of life cycles?
Characteristics of an animal in any one life cycle may improve its performance in one activity and reduce its performance in another
Where can major trade-offs be seen?
In animal reproduction
What are the trade-offs seen in animal reproduction?
Some animals produce large numbers of small eggs with small energy store,
The larger the energy store, the longer the offspring can develop before it must find its own food/be fed by parents.
What are the two types of young produced by bird species?
Altrical- eggs hatch when young and helpless, must be fed and cared for.
Precocial- incubated eggs for longer, hatchlings are able to forage immediately.
Give an example of precocial hatchlings
Canada Geese hatchlings- Branta canadensis
What do parasite life cycles do?
Evolve to facilitate dispersal and overcome host defenses
Why do parasites have to disperse?
To invade a new host
Because they die when their current host dies
What is the latin name of the broadfish tapeworm?
Diphyllobothrium latum
Explain the complex life cycle of the broadfish tapeworm among hosts.
Free swimming first larval stage is ingested by first intermediate host, copepod
Tapeworm develops in second larval stage and is ingested by first a perch and then a larger fish, before being eaten by mammalian host
What is bilateria?
A large, monophyletic group embracing all animals other than sponges, ctenophores and cnidarians
What traits support monophyly of bilateria?
Bilateral symmetry, three cell layers, presence of at least 7 hox genes
What are the two major categories of bilateria?
Protostomes
Deuterostomes
What are all animals except sponges called?
Eumetazoans
What are the features of eumetazoans?
Body symmetry, a gut, a nervous system, special types of cell junctions, well-organized tissues in distinct layers
What are sponges?
Simplest animals
What are some characteristics of sponges?
Some specialized cells but no cell layers or true organs, no body symmetry
What are spicules?
Skeletal elements which may be simple, complex, small or large
What evidence suggest that there are three groups of sponges?
Recent ribosomal RNA evidence
What are the three major groups of sponges?
Glass sponges, demosponges, calcareous sponges
What do glass sponges and demosponges have?
Skeletons composed of silicaceous spicules made of hydrated silicon dioxide
What do calcareous sponges have?
Calcium carbonate skeletons
What is the body plan of sponges?
An aggregation of cells built around a water canal system
How do sponges obtain food?
Water and food particles enter sponge by pores and pass into water canal
Choanocytes capture food particles.
How are sponge bodies supported?
A skeleton of simple or branching spicules, and a complex network of elastic fibers
How are sponge cells held together?
An extracellular matrix of collagen and adhesive glycoproteins and other molecules
How do sponges reproduce?
Both sexually and asexually- most individuals produce both sperm and egg but do not self fertilize
How do sponges asexually reproduce?
Budding and fragmentation
What are ctenophores also known as?
Comb jellies
What body plan do ctenophores have?
Radial symmetry, diploblastic, two cell layers
What are the two cell layers of ctenophores separated by?
A thick, gelatinous mesoglea
Why do ctenophores have low metabolic rates?
Because the mesoglea is an inert extracellular matrix
What type of gut do ctenophores have?
A complete gut
What are the 8 comb like rows of fused plates of cilia of ctenophores called?
ctenes
How do ctenophores move?
By beating cilia rather than muscular contractions
How do ctenophores feed?
Tentacles discharge adhesive material after capturing prey, tentacles retract and bring food to its mouth
What do ctenophores eat and where are they common?
small planktonic organisms
Open seas
What life cycle do ctenophores have?
Gametes are released into body cavity then discharged through mouth or anal pores, fertilization takes place in open sea, egg develops directly into miniature ctenophore.
What branch is below ctenophores?
Cnidarians
Name some common cnidarians.
Jellyfishes, sea anemones, corals, hydrozoans
What is the mouth of cnidarians connected to?
The blind gut, called the gastrovascular cavity
Why is the purpose of the gastrovascular cavity in cnidarians?
Digestion, circulation, gas exchange, hydrostatic skeleton
What are the two stages of cnidarians?
Sessile polyp stage
Motile medusa stage
What is the sessile polyp stage of cnidarians?
A cylindrical stalk is attached to the substratum
How do polyps form colonies?
By reproducing asexually by budding
What is the motile medusa stage of cnidarians?
Free-swimming shaped like a bell or umbrella, produces egg and sperm
What do fertilized eggs of cnidarians do?
Develop into free-swimming ciliated larva called planula which settle at the bottom do develop into polyp
How do cnidarians move?
Epithelial cells with muscle fibers whose contractions enable movement
Simple nerve nets integrate body activities
What specialized molecules do cnidarians have?
Collagen, actin, myosin
What type of feeder are cnidarians?
Predators
How do cnidarians act as predators?
Toxins on their nematocysts capture large complex prey
How do other cnidarians obtain additional nutrition?
Corals and anemones use photosynthetic protists that live in their tissues
What are cnidarians largely made up of?
Inert mesoglea- low metabolic rates mean they can survive environments with few prey
Where do cnidarians live?
All but a few in the ocean
Name the three major clades of cnidarians.
Scyphozoans, anthozoans, hydrozoans
Where do all scyphozoans live?
Marine
Why are scyphozoans called jellyfish?
Mesoglea of their medusa is thick
What life cycle dominates the scyphozoans?
Medusa
What are some members of the anthozoans clade?
Sea anemones, sea pens, corals
What are all sea anemones?
Solitary
What are sea pens?
Colonial
What do colonies of sea pens consist of?
Two kinds of polyps- primary and secondary
What do primary polyps do in colonies of sea pens?
Lower portion anchors to bottom sediment, branched upper portion produces secondary polyps by budding
What do secondary polyps do?
Some differentiate for feeding, others circulate water through the colony
What are characteristics of corals?
Sessile and colonial
How do most coral polyps form a hard skeleton?
By secreting a matrix of organic molecules on which they deposit calcium carbonate
Where do corals flourish?
Clear, nutrient poor tropical waters
Why does overabundance of nitrogen run off effect corals?
Gives an advantage to algae which smothers the corals
What life cycles do hydrozoans have?
Diverse- polyp typically dominates, but some have only medusae, others only polyps.
Are most hydrozoans solitary or colonial?
Colonial
What is the structure of a colony of hydrozoans formed by a single planula larvae?
Polyps all interconnected with a continuous gastrovascular cavity
What do some polyps in a colony of hydrozoans have?
Tentacles with many nematocysts to capture prey for the colony
What do some polyps in a colony of hydrozoans do if they are not capturing food?
Some are specialized for medusa production
Some are finger like and defend the colony with nematocysts
