Lecture 4 Diversity And Adaptation 1 Flashcards
Taxa and synapomorphies
Links based on understanding of shared derived traits aka synapomorphies which are often but not always structural as in traditional taxonomy.
Synapomorphies may be lost during evolution. Superficially similar traits can evolve independently aka convergent evolution. E.g. eyes in humans and cephalopods are actually phylogenetically diff
Animal (metazoan) monophylogenetic traits
Multicellular
Develop from zygote
Heterotrophic (ingest food)
Most move using specialised contractile muscle
Gene sequences e.g. ribosomal DNA support monophyly of animals
Similarity of hox gene function
Common extracellular matrix including collagen and proteoglycans
Hox genes
Specify regions of embryo for head to tail development in animals ensuring correct structures form in correct places in body
oposthokont eukaryotes
May have posterior flagellum e.g. animal sperm
Group includes fungi, choanoflagellates & animals
Similar to amoebazoans (amoeba)
Choanoflagellates have a collar of actin filled microvilli similar in structure to sponges
Colonial cells specialise for movement nutrition and reproduction
Coordination via chemical communication
Regulatory molecules decide differentiation & cell migration in embryo
Evolved in precambrian marine environment
Phylum Ponifera (sponges) 8000sp
Have some specialised cells - no layers or organs
Some can reform after pushed through sieve
Skeletal elements silica or CaCO3
Filter feeders ( sessile Cambrian organisms were too) use choanocyte cells similar to choanoflagellates to create water currents and capture food particles.
Almost all are marine only 50 fresh water species.
All sessile and grow on hard structures
No growth symmetry
Hermaphroditic but does not fertilise own cells.
Sperm carried in water currents
Radial cleavage in zygote in an even pattern (ancestral condition)
Phylum ctenophora and cnidaria
Radial cleavage - zygote divides in even pattern (ancestral condition)
Diploblastic: 2 cell layers (ecto and endoderm) separated by gelatinous acellular mesoglea that form in early embryonic development them differentiate to organs
Phylum cnidaria
Hydrazoans jellyfish, anemones and corals
~11000 species all aquatic most marine
Lack a complete gut - mouth connected to gastrovascular cavity used for digestion, circulation, gas exchange and hydrostatic skeleton
May be solitary or colonial typically have a life cycle w/platonic larvae dispersal + two other forms a sessile asexual polyp and a free swimming sexual medusa
Cnidaria tissue: Cnidocyte cells
Cnidaria have specialised cnidocyte cells contain nematocyst organelles which can inject toxin into prey. They can therefore be specialised predators though some are filter feeders
Cnidaria tissue: muscle and nerves
Muscle fibres arranged in sheets for movement, simple nerve nets integrate activity for predation
Nervous system and musculature is characteristic of most eumetozoans - sensory system linked to nerves and response through muscle
Prey capture by retraction of tentacles (anemone) or to escape predation
Cnidaria class Syphozoa
Small medusae bud off polyp and grow
Can be large but single organism
Painful sting by nematocysts
Cnidaria class Anthozoa
Sea anemone, sea pen, corals
Lack medusa stage
Polyp hermaphroditic egg>larvae development in polyp
Sea anemone are solitary polyps ( cand do slow limited movement)
Sea pens and corals are colonial and sessile typically predatory some are particle feeders.
Colonial forms contain polyps with diff roles for anchoring, feeding or reproducing
Cnidaria class Anthozoa - corals
Sessile and colonial - hard in warm soft in hot/cold conditions
Have organic CaCO3 matrix
As colony ages old polyps die but skeleton remains and is often overgrown by living corals forming reefs
Many coral species in warm but nutrient poor water enter endosymbiotic relationship with unicellular photosynthetic protists that live in polyp cells
Hard coral:
Easily damaged by nutrient build up from human waste, physical damage and climate change
Sensitive to water temperature slight but unusual increase causes expulsion of zooxanthellae causing bleaching and often resulting in polyp death
Diploblasts
Ctenophora cnidaria develop from 2 germ layers (regions of embryo giving rise to distinct forms of tissue.
Endo/ectoderm have radial symmetry
Triploblasts
Evolved from diploblasts
3 layer endo/miso and ectoderm
Bilateral symmetry (clade bilatera)
Associated with mouth end for food + co-evolved anteria specialisations to sense food, environment and threats
> Head development bilateral complex frontal sensory organs
Protostomes
8 cell stage spiral cleavage, left and right cleave asymmetric > schozocoelous solid masses of mesoderm split to form coleom > embryonic blastopore becomes the mouth.
