Download Animal Diversity - Invertebrates Read: Text ch 27 Bullet Points

Animal Diversity -­ Invertebrates
Read: Text ch 27
Bullet Points: • some defining properties of animals
• movement, symmetry & cephalization
• metazoa: sponges vs eumetazoa – tissues, muscle, nerve • multicellularity, tissues, immunity & cancer
• development – a tube within a tube
• which came 1st the mouth or the anus? • body plans & body cavities
• segmentation
• selected phyla: Sponge Bob and friends
• cnidaria – tissues-­ jellyfish • platyhelminthes – flat worms
• rotifers – and selection for sexual recombination
• mulluscs -­ snails, squid etc.
• annelids – fishing worms
• nematodes – round worms
• arthropods – crabs, spiders, insects -­ an inordinate fondness for beetles
• echinoderms – starfish (secondarily radial)
• chordates – some of your best friends
You should know
the classification,
“body plans”
patterns of development
and other properties
of the cast of -­
Richter, D.J. and King, N. (2013) The genomic
and cellular foundations of animal origins.
Annual Review of Genetics. 47: 509-537.
What is an Animal?
(Metazoa). 1. Multicellular, heterotrophic, eukaryotes, w/o cell walls, that ingest food collagen (‘gut’)
is most abundant
protein in vert. body
2. Cells a) lack cell walls (ch 4)
b) supported by extracellular matrix: (ch 4.7)
proteoglycans, glycoproteins, integrin & collagen
c) unique intercellular junctions: Fig 4.26 integrate tissues (except Porifera) 3. Nervous tissue & muscle tissue
(except Porifera)
4. Life history (mostly):
diploid dominates, sexual w/ small flagellated sperm & large immobile egg;; cleavage, blastulation, gastrulation … ch 36.7:
+. Glycogen: carbohydrate store
(like fungi) Fig. 5.6:
Body plans:
Symmetry
see text Fig 27.5
[a protist]
Most animals that move actively are bilateral. adult echinoderms
Bilateral symmetry
and some mollusks
is associated with
lose juvenile
cephalization, bilateral symmetry
concentrating sensory equipment when they grow into
sedentary adults
on the cephalic [head] end, that is usually first to encounter food, danger, and other stimuli. Cephalization also includes a central nervous system concentrated in the head …
Many radial animals are sessile forms
(attached to a substratum) or plankton (drifting or weakly swimming aquatic forms). They meet the environment equally well from all sides. *
*
*
Monophyletic origins of the metazoa: an evolutionary link with fungi.
Wainright et al. Science 1993 Apr 16;;260(5106):340-­2
… comparisons of small subunit ribosomal RNA sequences describes the evolutionary origin and early branching patterns of the kingdom Animalia …
animals & fungi share a unique evolutionary history and that their last common ancestor was a flagellated protist similar to extant choanoflagellates.
Sponges are Metazoa,
but they have only a few cell types differentiated to perform specialized functions;; they lack the cell-­to-­cell junctions that form sheets of integrated tissues in Eumetazoa. Most sponges
are sequential hermaphrodites,
and can reproduce asexually
by breaking off clones
The [sponge] Amphimedon queenslandica genome and the evolution of animal complexity
M Srivastava et al Nature 466, 720–726 (05 August 2010)
The emergence of multicellular animals from single-­celled ancestors over 600  million years ago required the evolution of mechanisms for coordinating cell division, growth, specialization, adhesion and death. Dysfunction of these mechanisms drives diseases such as cancers, in which social controls on multicellularity fail, and autoimmune disorders, in which distinctions between self and non-­self are disrupted.
Metazoan multicellularity [is] intimately related to cancer and immunity.
Sponges [are] the oldest surviving metazoan phyletic lineage. Sponges share key adhesion and signalling genes with eumetazoans, …
[ cellular communication and “social behavior” ]
Comparison of the A. queenslandica draft genome with sequences from other species can provide [an] estimate of the genome of the common ancestor of all animals …
The A. queenslandica genome allows us to assess the origin of the six hallmarks of metazoan multicellularity: (1) regulated cell cycling and growth;; (2) programmed cell death;; (3) cell–cell and cell–matrix adhesion;; (4) developmental signalling and gene regulation;; (5) allorecognition and innate immunity;; and (6) specialization of cell types.
A recurring theme is the overlap [90%] of these core ‘multicellularity’ genes with genes perturbed in cancer, a disease of aberrant multicellularity.
http://science.sciencemag.org.proxy1.cl.msu.edu/content/351/6280/1378.full
http://www.nature.com/news/penis-­worm-­pokes-­holes-­in-­evolutionary-­dogma-­1.11667
a major step in evolution occurred when an embryonic ball of cells The N&V grading rubric says formed two indentations “The title needs to be intriguing and as opposed to one, giving way to a little bit cute but not too cute ...” a separate mouth and an anus What do you think about this title?
rather than the single opening that creatures such as jellyfish and sea anemones have. In 1908, animals with a mouth and anus were divided into two groups. In the protostomes, the mouth formed first, and the anus second. In the the deuterostomes
the mouth formed second
A study of gene-­expression in priapulids or ‘penis’ worms throws doubt on … the [phylogenetic identity of] protostomes. [not a clade]
... the priapulid Priapus caudatus, develops like a deuterostome. Evolutionary biologists will need to rename the protostomes. {instead, they have dumped protostome as a phylogenetic lineage
– we still have the deutrostome clade – echinoderms, chordates}
Patterns of development in bilateria:
“other things”” vs Deuterostomes
chordates & echinoderms
gut
is not a
body cavity,
it’s a tube
coelom
lined w/
mesoderm
is a body cavity
Vertebrates are Chordates which are segmented, bilateral Deuterostomes,
“identical twins” up to 16 cells
so you should understand basic deuterostome development & structure -­ more on development in a later lecture
Patterns of development in bilateria: Body Cavities -­
Coeloms
phylogenetically, these are all
in the Bilateria Coelomate clade,
but some have lost the coelom
& some lose bilateral symmetry
The molecular-­based phylogeny (Fig 27.5) suggests that the bilateral animals are a monophyletic group with true coeloms. {coelom is shared derived trait in bilateria clade}
Bilaterians lacking coeloms (acoelomates -­ flatworms) & those w/ pseudocoeloms
(not completely lined by mesoderm -­ roundworms) evolved secondarily from coelomates. Peritoneal dialysis
http://www.sciencedaily.com/releases/2010/07/100726222316.htm
Segmentation Is the Secret Behind
the Extraordinary Diversification of Animals
ScienceDaily (July 27, 2010)
Segmentation, the [modular] repetition of anatomically similar units along the axis running from the front to the rear of their bodies, seems to be the secret behind the diversity of the largest and most common animal groups on Earth …
annelids, arthropods and vertebrates
These three groups are not closely related to one another. {and not all lineages of bilateria are visibly segmented}
Is it possible that they all inherited this feature from a very distant common ancestor …?
{and some lineages of bilateria lost segmentation?} Or has segmentation occurred several times during the history of evolution?
The researchers found that the genes controlling segment formation during embryo development are almost the same in drosophila and in annelid worms.
These similarities led them to conclude that the genes had been inherited from a common ancestor …supports the idea that segmentation only appeared once in the history of evolution … {shared derived}
Hedgehog Signaling Regulates Segment Formation in the Annelid Platynereis
N Dray et al. Science 16 July 2010: 339-­342. Hedgehog proteins first arose in the common ancestor of Cnidarians and the bilateria
more than 650 million years ago [orthologous homologs across eumetazoa;; then multiple paralogs evolved within lineages – HOX genes]
Cnidaria are exclusively aquatic, radially symmetrical,
w/ true tissue sheets [therefore Eumetazoa], uncephalized (no head w/ brain)
with a single body opening, the mouth;; the gut is not a ‘body cavity’ inside mesoderm.
polyps such as hydra, anemones & corals {mouth up}.
medusae such as jellyfish {mouth down},
http://www.nikonsmallwo rld.c om/ gall ery. ph p?g ro upin g=y ea r&ye ar =19 86&i mag ep os= 1
Lophotrochozoa [don’t memorize the name] is a clade identified by molecular data;;
Platyhelminthes (flatworms)
The simplest animals that are bilaterally symmetrical and triploblastic (3 cell layers) a) Non-­parasitic Tubellarians:
Freshwater
Planeria
Marine
flat worms
c) Trematode b) Monogenean flukes
fish parasites:
d) Cestode
tapeworms:
Rotifers are tiny aquatic animals
with an anus!
{a big evolutionary breakthrough} Some species of rotifers have no males -­ or sex!
more on this next slide
The Evolution of Sex Is Favoured During Adaptation to New Environments
Lutz Becks , Aneil F. Agrawal PLOS Published: May 1, 2012
For well over a century, biologists have wondered why sex is such a common mode of reproduction, given the immediate 2-­fold fitness cost entailed by the reduced number of [female] offspring per parent. The most classic explanation is that sex is favoured because it helps to generate the variation necessary for adaptation. While theoretical models support this idea, there are no direct experimental data and it is far from obvious whether any such advantage could balance the considerable costs of sex. Using experimental populations of a facultatively sexual species of rotifer, we demonstrate that rates of sex evolutionarily increase as populations adapt to novel environments. We show that sex creates a diverse array of genotypes, including many that are quite unfit [lots of losers, quickly lost from population] but also others that are very fit in the new environment. [a few that win big ]
The average fitness of these sexually derived offspring is lower than that of asexuals, but those [few] well-­adapted genotypes generated by sex contribute disproportionately to future generations, causing the genetic propensity for sex to ultimately increase.
Mullusks
Bilateria, NOT Deuterostomes
Most spp have distinct sexes
but many snails are hermaphroditic Major Classes of Phylum Mollusca
(chitons) Marine;; Gastropods (snails) Marine, freshwater, or terrestrial;; [secondarily] asymmetric body,
[larval bilateral symmetry lost in “creepy” adults]
usually with a coiled shell;; foot for locomotion;; radula present
Bivalves (clams, mussels, scallops, oysters) Marine and freshwater, flattened shell with two valves;; head reduced;; filter-­feeders [larval bilateral symmetry lost in sedentary adults]
Cephalopods (squids, octopuses, chambered nautiluses) Marine;; head surrounded by grasping tentacles, usually with suckers;; locomotion by jet propulsion using siphon made from mantle. – active, bilateral symmetry
great eyes {part homology, part analogy}, very smart!
Annelids are Bilateria, NOT Deuterostomes, w/ true coelom
& segmentation
A forest floor without worms (left) and with (right). Spring flowers and tree seedlings both suffer when earthworms munch the decaying litter on the ground. Courtesy University of Minnesota, Agricultural Experiment Station
Earthworms are a blessing in gardens, where they mix the soil, increase porosity,
and leave fertile droppings … But … it's not true in ecosystems that are not "used to" worms.
In the upper Midwest, all worms were extirpated
by Ice-Age glaciers that smothered the area until about 11,000 years ago.
And since worms can't travel far under their own steam,
the forests have had essentially no worms. {for over 11,000 years}
In contrast, worms reached cities and farms courtesy of settlers who brought plants and soil).
Effects of Earthworm Invasion on Plant Species Richness in Northern Hardwood Forests. A.R. Holdsworth et al. 2007. Conservation Biol 21:997-­1008. Nematodes (“roundworms”) among the most widespread of all animals,
found in most aquatic habitats & soil, plant & animal tissue (parasites) nematodes are major crop pests
{Ecdysozoa (forget the name) – tough cuticle}
Bilaterally symmetrical,
NOT Deuterostomes, human hookworms include not segmented {segmentation lost}.
two nematode (roundworm) species
-­leading causes of maternal & child morbidity in the tropics
Nematodes possess digestive, nervous, excretory, & repro systems, but lack a discrete circulatory or respiratory system.
Their digestive system has two openings Why we don’t eat pork rare:
-­ at the mouth and anus. {which 1st?}
Trichinella spiralis
Muscle Biopsy
1. ‘jointed feet’
2. exoskeleton 3. segmentation
The body of an arthropod is completely covered by the cuticle, an exoskeleton from layers of protein and chitin. {not cell walls}
Cephalization is extensive, w/ well-­developed sensory organs, including eyes, olfactory receptors, and antennae for touch and smell & ventral nerve cord. http://www.economist.com/news/science-­and-­technology/21646647-­why-­are-­there-­so-­many-­species-­coleptera-­beetlemania
Echinoderms – marine bottom crawlers -­
The radial body organization in sessile (‘slow’) adults is secondary.
Echinoderms are in the bilateria clade, and
active Echinoderm larvae are bilateral.
”Creepy” adults lose bilateral shape. The Chordates, [next lecture]
to which we belong, consists of two subphyla of invertebrate chordates {Urochordates & Cephalochordates}
plus the subphylum Vertebrata, the animals with backbones.