Lecture 9- Animal origins and the evolution of body plans I Flashcards
What traits distinguish animals?
- All multicellular (undergo development from a single cell)
- All heterotrophs, use internal digestion processes
- Most move- specialized muscle tissues
What supports the theory that animals are monophyletic?
Gene sequences and morphology:
Similar organization and function of Hox genes
What do hox genes do?
Control body plan
Why can’t syanomorphies be used to infer relationships?
Because all animals have them
What are two other syanomorphies of animals?
- Unique cell junctions
- Common set of extracellular matrix molecules
What are the unique cell junctions in animals?
Tight junctions, desmosomes, gap junctions
What are some of the common extracellular matrix molecules in animals?
Collagen, proteoglycans
Why don’t some animals have traits that are syanpomorphies?
They were lost during their development
What was the most likely ancestor to the animal clade?
Colonial flagellated protist
How did animals first begin to evolve from a colonial flagellated protist?
Functional specialization of cells in the colony arose (e.g. movement, nutrition, reproduction), cells continued to differentiate
How was coordination among the original colonial flagellated protists from which the animal clade arose improved?
Regulatory molecules to control gene differentiation and migration of cells, leading to larger, more complex animals
How are evolutionary relationships within the animal clade studied?
Using differences in derived traits
What are the three main groups that all animals belong to?
Sponges, diploblastic animals, bilaterians
What two groups are bilaterians divided into?
Protostomes and deuterostomes
How are patterns of embryonic development used to study evolutionary relationships?
Cleavage patterns distinguish some animal groups
What are cleavage patterns?
The first few divisions of the zygote
How is the division pattern of a zygote influenced?
Configuration of the yolk
What does cleavage do?
Increases number of cells and nuclear mass
Not cytoplasmic mass
What are the cells derived from cleavage called?
Blastomeres
What type of cleavage is seen in sea urchins and other echinoderms?
Complete radial cleavage
What is the ancestral condition of cleavage for eumetazoans?
Complete radial cleavage
What group of animals have spiral cleavage?
Lophotrochozoans
What is spiral cleavage derived from?
radial cleavage
Name two organisms in which spiral cleavage can be seen.
Clams
Earthworms
Complete cleavage is also called…
Hobloblastic cleavage
What is incomplete cleavage called?
Meroblastic cleavage
In what animals is meroblastic cleavage seen and why?
Reptiles- due to presence of large yolk
What are eumetazoa?
All animals except sponges
What are lophotrochozoans with spiral cleavage sometimes referred to as?
Spiralians
What happens during early development of most animals?
Distinct layers of cells form
What happens to the distinct layers of cell that form during early embryo development?
They differentiate into specific organs and organ systems as development continues
What are embryos with two cell layers called?
Diploblastic
What two cell layers do diploblastic organisms have?
Outer ecoderm
Inner endoderm
What cell layers do triploblastic organisms have?
Outer ecoderm
Inner endoderm
Middle mesoderm
What is the ancestral condition of cell layers?
Diploblastic
What animals show the ancestral condition of cell layers?
Ctenophores and cnidarians (paraphyletic)
What happens during early development in many animals?
Gastulation
What is gastrulation?
A hollow ball one cell thick indents to form a cup shaped structure
What is the opening of the cavity formed by an indentation of the hollow ball formed during early development called?
The blastopore
In what animals does the blastopore develop into a mouth first, with the anus forming later?
Protostomes
What is the ancestral condition for blastopore development?
Deuterostomes
What are the three major clades of deuterostomes?
Chordates
Hemichordates
Echinoderms
What type of cleavage is seen in most deuterostomes?
Indeterminate cleavage
What is the body plan of an animal
The general structure, arrangement and integrated functioning of an animal
What 4 key features make up an animal body plan?
Symmetry of body
Structure of body cavity
Segmentation of body
External appendages
What governs the development of an animals body plan?
Regulatory genes
What does symmetry describe?
The overall shape of an animal
What animals are asymmetrical?
Sponges
What is the simplest form of symmetry?
Spherical symmetry- body parts radiate out of a central point
Where is spherical symmetry seen?
Many unicellular protists
What is radial symmetry?
When there is one main axis around which body parts are arranged
What two animal groups are composed mainly of radially symmetrical animals?
Ctenophores
Cnidarians
How are most radially symmetrical animals modified?
So that fewer planes can divide them into idential halves
Give examples of radial symmetry that has been modified.
Starfish
Sand dollars
How do most radially symmetrical animals move?
Either sessile
or move equally well in all directions, slowly.
What is bilateral symmetry a characteristic of?
Animals that move in one direction
What is bilateral symmetry?
Animals that can be divided into mirror images by a single plan passing through the midline of its body
What two planes does a plane at right angles to the midline divide the body into in bilaterally symmetrical animals?
The dorsal (back) Ventral (mouth and belly)
From what point to what point does the plane that divides bilaterally symmetrical animals run?
From the anterior to posterior
What is bilaterally symmetry associated with?
Cephalization
What is cephalization?
The concentration of sensory organs and nervous tissues in a head at the anterior end of the animal
What has cephalization been evolutionary favoured?
The anterior end of a bilaterally symmetrical animal typically encounters new environments first
What three types can an animal be divided into based on the structure of its internal, fluid filled body cavity?
Acoelomate
psuedocoelomate
coelomate
What does the structure of an animals body cavity strongly influence?
The way it can move
Give an example of an acoelomate animal.
Flatworm
What are acoelomate animals?
Animals which lack an enclosed, fluid-filled body cavity
What do acoelomate animals have instead of a body cavity?
Space between gut and muscular body wall is filled with masses of cells called mesenchyme
What tissue layer is the gut derived from?
The endoderm
What tissue layer is the muscular body wall derived from?
The mesoderm
How do acoelomate animals typically move?
By beating cilia
What do psuedocoelomate animals have?
A body cavity called a psuedocoel
What is a psuedocoel?
A fluid filled space in which many internal organs are suspended
What is the psuedocoel enclosed by?
Muscles (medoderm) only on the outside
No inner layer of mesoderm surrounding internal organs
What do coelomate animals have?
A coelom
What is a coelom?
A fluid filled cavity that develops within the mesoderm
What is the coelom lined with?
A layer of muscular tissue called peritoneum, which also surrounds internal organs
What do a coelomate animal have that a psuedocoelomate animal does not?
Better control over the movement of fluids in its body cavity
What do body cavities of many animals function as?
A hydrostatic skeleton
How do body cavities function as a hydrostatic skeleton?
Fluids are relatively in-compressible
Muscles surrounding fluid contracts, they move to another part of the cavity
Fluid squeezed to one region makes it expand to move body parts
What type of muscles do animals have that gives them better control over their body?
circular muscles (encircling body cavity) Longitudinal muscles (running along length of body)
What do most animals have to provide protection and facilitate movement?
Skeletons
What is attached to skeletons?
muscles
What does segmentation do?
Facilitates the specialization of different body regions,
alter body shape in complex ways
control complex movements precisely
What do muscles do when an animal is segmented?
Muscles in each segment can change the shape of that segment independently of the others
What only occurs in few animals?
Complete segmentation
What does even partly segmented compartments allow for?
Better control of movement
Give an example of an animal with an evenly segmented body plan.
Hermodice carunculata
marine fireworm
What type of animal does the Hermodice carunculata belong to?
Annelid
What appendages does the marine fireworm have?
Simple brushes (setae)
What is the function of setae in the marine fireworm?
Mainly protection- they contain noxious toxin
Give an example of an animal which has segments with different modifications.
Orconectes williamsii
How did segmentation evolve?
Independently several times in both protostomes and deuterostomes
In what animals is segments not visible externally?
Vertebrates, where vertabrae are segmented internally
What led to the dramatic evolutionary radiation of arthropods?
Changes in segmented body plan (including muscles attached to external skeletons) and the variety of appendages
What do appendages do?
Enhance locomotion
What does locomotion enable?
Obtain food, avoid predators, find mates
What appendages do sessile sea anemones have and why?
Larval stages with cilia to swim- increase chances of finding suitable habitat to settle
What do many echinoderms have?
Tube feet
Give examples of animals with tube feet.
Sea urchins, sea stars
What do tube feet allow echinoderms to do?
Move slowly across substratum
What do limbs allow?
Highly controlled, rapid movement
In what two animal groups can jointed limbs be seen?
Arthropods
Vertebrates
What was a prominent factor in the evolutionary success of arthropods and vertebrates?
Jointed limbs
How were limbs modified into wings?
In several independent instances among arthropod insects, pterosaurs, birds and bats
What has the need to locate food favored?
Evolution of sensory structures to provide detailed info. on environment
Nervous systems that receive/process/coordinate info
What are the 5 broad categories of feeding strategies?
Filter feeders Herbivores Predators Parasites Detritivores
What is required to be expended to obtain food?
Energy
How do filter feeders obtain food?
Some kind of straining device filters food from the environment
What do air and water contain?
Small organisms/ organic molecules that are potential food
How do sessile aquatic animals obtain their food through filter feeding?
Water currents bring prey
Give an example of a motile filter feeder?
Phoenicopterus ruber
Flamingo
Explain how a flamingo feeds.
Serrated beak filters small organisms out of a muddy mixture it picks up as it wades through shallow water
How do some sessile filter feeders expend energy?
By moving water past food capturing devices
Give an example of a sessile filter feeder moving water past food capturing devices
Sponges bring water to their bodies by beating flagella of specialized feeding cells called choanocytes
What are choanoflagellates and the animals most closely related to what clade does this make up?
Fungi and choanoflagellated protists
Opisthokonts
How are herbivores different to carnivores, other than what they eat?
Herbivores often feed on plants without killing them
What is an advantage of herbivory?
Animals do not need to expend energy capturing and subduing plants
What is a disadvantage of herbivory?
Plants can be difficult to digest- many different kinds of tissues, fibrous, chemicals that need to be detoxified
What herbivores feed on the single plant, the silky willow?
Tiger swallowtail butterfly larva
Adult leaf beetle
Willow sawfly larvae
Leaf beetle larvae
What adaptations to predators have to make them able to capture and subdue relatively large animals?
Sensitive sensory organs
Sharp teeth/claws
toxins
How do cnidarians capture and subdue prey?
toxins- tentacles are covered with specialized cells containing stinging organelles called nematocysts which inject toxin into prey
Give an example of a predator whose teeth are adapted to its omnivorous diet.
Ursus arctos
Kodiak brown bear
Give an example of a predator whose appendages and beak are adapted to life as a predator.
Bald eagle
What is the function of sylets and spines on a nematocyst?
To anchor it to its prey
Give an example of an animal that has nematocysts
Physalia physalia
Portuguese man-of-war
What are parasites that live inside their host called?
Endoparasites
What are endoparasites usually like?
morphologically simple function without digestive system
What are parasites that live outside of their host called?
Ectoparasites
Give an example of two ectoparasites of humans.
Fleas
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