Lecture 15 Flashcards
Invertebrates
Animals without a vertebra (backbone)
All animals except for a portion of chordata are invertebrates
Traits specific for vertebrates
Backbone
Hinged Jaws
Limbs with digits
All members of Eumetazoa has
a digestive tract and differentiated tissues
Invertebrates have
incredible diversity in shape and form
Huge mixture of homologous and analogous traits as they developed, got inherited and lost in different lineages of animals
Bilateria
Animals with bilateral symmetry
Lophotrochozoa - animals with bilateral symmetry
are exclusively invertebrate
Lophophore: crown of ciliated tentacles for feeding
Trochophore larva: Developmental stage which some animals go through
Ecdysozoa - animals with bilateral symmetry
Invertebrate
Many members have cuticle exoskeletons for protection and support
Moulting/ecdysis: Animals shedding its old exoskeleton to grow larger ex: dragonfly
Deuterostomia
Some Invertebrates
- Starfish, chordata which include vertebrates
Examples of Lophotrochozoans
- flatworm
- Tapeworm
- Mollusca: snails
Earthworms
Molluscs
Second most diverse phylum of animals after arthropods
- snails, slugs, clams
Mostly marine with some freshwater and terrestrial species
Soft bodied animals
- Many members excrete a hard shell made of calcium carbonate… These shells are lost or internalized in other species
Mollusc body
Foot: Movement and attachment
Visceral mass: Contains most of the inner organs
Mantle: Covers the visceral mass and secretes the shell
The mantle extends beyond the visceral mass to create the mantle cavity (An open space which contains gills, anus)
Bivalves
Aquatic suspension feeders such as clams, oysters, mussels
Two shells (bi-valves) connected by a hinge and strong muscle(s) close them tightly
Low mobility - swim by flapping valves
How do bivalves use gills for feeding and gas exchange
Water inhaled from the incurrent siphon into the mantle cavity and pumped out from the excurrent siphon
Gills trap food as water passes through gills
Cephalopods
Aquatic hunters such as an octopus and a squid
Mantle is on the outer surface (shells minimized, internalized or lost)
Foot has evolved into tentacles and parts of the excurrent siphon
How do cephalopods draw water into the mantle cavity through the incurrent siphon
Contracts mantle to release water jet from the excurrent siphon, propelling the animal
The muscular siphon can be pointed towards different positions
Chromatophores on the squid skin facilitate
Camoflauging and/or signaling
Ecdysozoans
Most species rich animal group
- Nematodes, centipedes
Contains more species than all other animal, protist, fungus and plant groups combined
Exoskeleton is made of cuticle
“ One who does ecdysis”
- Molting is part of many members development
Nematodes
Worms, found in many habitats
- Aquatic, soil, moist tissues of plants, body fluids and tissues of animals
Many are free living, others parasitic
- Trichinella spiralis is the muscle burrowing parasite found in pork
Caenorhabditis elegans - nematode
An adult has 959 or 1033 cells depending on gender
Exact locations as well as their developmental pathways for all cells has been mapped
Model organism for biology in various developmental and medicinal fields of research
Arthropods
Crustaceans (crabs, lobster), milipedes, insects etc
- Mainly inhabit aquatic environmentals
- Insects dominate terrestrial environments
Arthropod body
Segmented body with jointed appendages attached (making antennae, pincers, legs)
Pair of compound (multi lens) eyes
All body parts coated with cuticle even the joints
- Molting is necessary for growth… is very expensive and dangerous for animal
“soft shelled crabs” are crabs which have just moulted and has a soft shell
Insects
Huge diversity
Many members co-evolved with specific plant species especially angiosperms as pollinators (mutalistic relationship)
Plants provide insects with nutrients (nectar) to flourish on land
Insects pollinate the flowers
Insects body
Segmented body
- Head
- Thorax
- Post genital region
Three pairs of legs on the ventral side of thorax
Usually one or two pairs of wings on the dorsal side of the thorax (wings are extensions of cuticles)
- Can still have 3 pairs of legs while having wings
Incomplete metamorphosis
Insect larva develop into adult form via metamorphosis
Incomplete metamorphosis: grass hoppers, dragonflies
- Gradual growth of larva into adult via multiple moutling
Young nymphs resemble adults but are immature and can be smaller with different body proportions
nymphs go through
multiple moults every time becoming closer to the adult
Complete metamorphosis
- Distinct stepwise growth of larva into adult via a pupal stage
- wasps, bees, butterflies
Larval stages specialized for eating and looks completely different from the adult - Adult is specialized for dispersal and reproduction
Metamorphosis from the larval stage to the adult occurs during the
pupal stage
Larval tissues are
broken down completely and the adult body is made new
Metamorphosis of butterfly
Larvae -> pupa -> Later stage pupa -> emerging adult -> adult
