BIOL 371 Theme 2

Monophyletic

An ancestor and all it’s decendants

Polyphyletic

The most recent common ancestor is not included. Bad.

Paraphyletic Taxon

Some decendants of the common ancestor are excluded ex. Reptiles excluding birds

Opisthokonts

Animals, fungi, choanoflagellates

Choanoflagellates

Single or colonial set of cells. Flagellated and small

Where do plants and Opisthokonts separate?

Before fungi. Heterotrophy vs autotrophs is the prime separation point with Opisthokonts being heterotrophs.

First step of gastrulation

Colonial protist with flagella

Second step of gastrulation

Hollow sphere (Blastula) of unspecialized flagellated cells

Third stage of gastrulation

Certain cells become specialized for feeding and other functions

Fourth stage of gastrulation

Feeding cells fold in producing a two layered animal with a gastrula

Features of Opisthokont animals

• Multicellular eukaryote

• Chemoheterotrophic

• No cell walls

• Motile at some life stage

• Oxydative phosphorylation

• Sense and respond to environments

• Dominant diploid stage, haploid stage short lived

Opisthokont diagnostic characteristics

• develop a blastula

• Certain extra cellular matrix molecules (ex. Proteoglycam complex)

• Certain cell-cell membrane junction

Anchoring Junction (Adherence Junctions)

Adhere at mass of proteins anchored beneath membranes by many intermediate filaments, how cells stick together

Tight junction

Form between adjacent cells by fusion of plasma membrane proteins of their outer surface. Complex network that makes a tight seal. Prevents leaking

Gap junction

Cylindrical arrays of proteins that form direct channels that allow small molecules and ions to go between cells

Plant characteristics

• multicellular eukaryote

• Photoautotrophic

• Cell walls

• Sessile

• Alternation of generations lifestyle

Where did plastids come from in plants

Secondary endosymbiosis (ex. Photosynthetic sea slug (eats Cyanobacteria), spotted salamander)

Mobility in plants

• direction of growth

• In response to physical touch (Venus flytrap)

• Dispersing seeds or pollen

Mobility in animals

• Chemoheterotroph

• Eat things to acquire energy and carbon

• Must be mobile to acquire food

Animal movement hierarchy

• muscles act on skeletons

• Nervous system required for signals

• Digestive system required for energy

• Excretory system

• High metabolic rate

Sessile animals

• barnacles, coral, muscles (filter feeders)

• Tube worms (chemoautotrophs)

Divergence between Opisthokonts and plants

• animals are diploid at dominant life stage

• Plants alternate between haploid gametophyte and diploid sporophyte

Cnidaria, Placozoa, ctenophores

• Diploblastic

• Radial symmetry

Sponges

• no tissues

• No symmetry

Protostomes

• mouth first (blastopore becomes mouth)

• Triploblastic

• Bilaterally symmetrical

Deuterostomes

• mouth second (blastopore becomes anus)

• Triploblastic

• Bilaterally symmetric

3 layers of triploblasts

Ectoderm, mesoderm, endoderm

Colinearity

Spatial organization of hox clusters directly comparable to spatial organization of expression pattern in body

Acoelomate

No body cavity separates the gut and body wall

Pseudocoelomate

Forms between gut and emdoderm

Coelomate

Completely lined coelom by a derivative of the mesoderm

Protostome cleavage

Spiral/determinant cleavage. Twist during division.

Determinant cleavage

• occurs in protostomes

• Each cell is determined what it will be early on

Deuterostome cleavage

• radial cleavage

• Straight division

• Indeterminant

Indeterminant cleavage

Don’t have specialized role. Drifts then specialized

Coelom development protostomes

Mesoderm makes two sacs next to the gut. Schizocoelom

Coelom development deuterostomes

Mesoderm makes “ears” that pinch off into coelom. Enterocoelom

Ectoderm

Develops into skin

Endoderm

Develops into gut lining and lungs

Mesoderm

Develops into bones and muscles

Protostome features

• spiral cleavage

• Schizocoelous coelom

• Blastopore forms mouth

• Determinant cleavage

• Ventral nerve chord that anteriorally surrounds digestive tract

Deuterostome features

• radial cleavage

• Enterocoelous coelom

• Blastopore forms anus

• Inderterminant cleavage

• Dorsal nerve chord

Lophotrochozoans

Lophophor feeding structure - filter feeders

Trochophore larvae - mobile intestinal tract

Ecdysozoans

External cuticle that is shed to grow

Body segmentation

Repeating: meta metric ( chordates, arthropods, earthworms/leeches)

Ctenophora

• comb jellies (combs are fused cilia)

• Gelatinous bodies

• Combs are used in movement

Porifera

• sponges

• Asymmetrical

• No true tissues (parazoans)

• Sessile as adults

• Filter feeders

Cnidaria

• jelly fish, anemones, hydra

• Radial symmetry

• Diploblastic

Body forms of radial animals

Polyp (upright mouth) - corals, anemones

Medusa (downturned mouth) - jellyfish

Cnidocytes and Nematocysts

Nematocyst fires and stings with contact

Phylums within Lophotrochozoa

• Platyhelmines (flatworms)

• Annelida (segmented worms)

• Molluscs (snails, clams, squid)

Phylum’s within Ecdysozoa

• Nematoda (roundworms)

• Arthropoda (insects, spiders, crustaceans)

Rotifera

• sister group to lophotrochozoa

• Rotifers

• Have a ciliates mouth that brings water in.

• Grinding mast ax behind mouth

Platyhelminthes

• flatworms

• Lost coeloms (don’t need it for locomotion)

• Mostly parasitic

• No gut as steal already digested food

• No circulation (use diffusion)

Mollusca

• diverse (100000 species, 1mm to over 18m)

• Have headfoot (food clearly associated with head)

• Visceral mass (where the guts are)

• Mantle (what generates shell)

Annelida

• Segmented worms

• Obvious segmentation

• Use coelom as movement (like water balloon)

Nematoda

• Roundworms

• 20000 species

• Ubiquitous

• Parasites and pests

• Have pseudocoelom

• Mostly microscopic

Arthropoda

• exoskeleton

• Segmented body

• Jointed legs

• Developmental stages defined by moults (instars)

Deuterostomes

• Echinodermata (starfish, urchins)

• Hemichordata (acorn worms)

• Chordata (urochordata, cephalochordata, vertebrata)

Echinodermata

• Bilaterally symmetrical larvae

• Pentaradiate as adults

• Water vascular system and tube feet

• Spiny skin

Phylum Hemichordata

• Acorn worms

• Have a stomochord (stiffens body) not notochord

• Pharyngeal gill slits

• Dorsal nerve chord

Phylum Chordata

• notochord (forms first)

• Dorsal, hollow nerve cord

• Pharyngeal gill slits

• Segmented muscles with post anal tail

Subphylum Cephalochordata

• Subphylum of chordata

• Lancelets

• Ancestral chordate

• Pharynx feeds right into gut

Phylum Chordata: Urochordata

• obvious Chordate at larval stage

• Almost coral-like as adult

• Tea-pot like structure

Urochordate Metamorphosis

Motile as larvae, undergo metamorphosis as adults and settle within 20 days

Phylum Chordata: vertebrata

• segmented brain

• Sensory placodes

• Branchial arches

• Medial fins

Neural crest cells

In vertebrata

Formed from ectoderm

Come from neural crest and disperse to form all body structures

Features of all Plant cells

• Primary cell wall

• cellulose fibres in matrix of hemicellulose

• Rigid but flexible

Plant cell wall structure

Cellulose (unbranched), structural protein, hemicellulose (branched), pectin

Secondary cell wall

• xylem, sclerenchyma

• Cellulose fibres anchored with lignin

• Stronger

• Waterproof barrier

• Not all plants

Hypertonic solution

Cell shrinks - h2o goes out - plasmolysed

Isotonic solution

Cell remains same size - flaccid - intermittent plasmolysis

Hypotonic solution

Turgid cell - swells - enters cell

Central vacuole

Occupies 90% of cell, inflates like a balloon

Defining characteristics of land plants

• eukarya

• Almost all photoautotrophs

• Multicellular

• Cell walls

• Sessile

• Alternation if generations

• Retained embryo in female gametophyte

Alternation of generations

Alternate between haploid (gametophyte), and diploid (sporophyte)

Diploid phase

Sporophyte

Haploid phase

Gametophyte

Sporophyte

• diploid

• Multicellular

• Produces spores through (n) meiosis

Spores

• haploid

• Unicellular

• Germinate to produce gametophyte (n) through meiosis

Gametophyte

• haploid

• Multicellular

• Produces haploid unicellular gametes (n) through mitosis

Embryo

Diploid, multicellular

Vascular tissue

Circulatory system that addresses plant ans nutrient needs

Fiber cells

• sclerenchyma cells

• Provide rigid support to xylem and phloem

Xylem

• rigid - strengthened by lignin

• Water conducting cells

• Dead at maturity

Phloem cells

• transport sugars and other solutes

• Soft

• Live

• Sandwiched by xylem and schlerenchyma for protection

Nonvascular plants

• lack vascular tissue

• Dominant haploid generation

• I.e bryophytes (mosses)

Vascular seedless plants

• well developed vascular tissues

• No seeds

• Dominant diploid generation

• Lycophytes and pterophytes (ferns)

Vascular seed plants

• well developed vascularature and seeds

• Dominant diploid generation

• Microscopic/small haploid generation

Why is staying in a gametophyte phase good and bad?

Accumulate more mutations but those can be delatirious

Bryophytes

• mosses

• First to appear on land

• No vascular tissues

• Small and close to the ground

• Poikilohydric

Poikilohydric

• variable water

• Little control of internal water content

• Don’t restrict water loss

• Drought tolerators (osmatic adjustment and cell wall elasticity)

Filamentous protonema

Spores germinate and produce protonema

Rhizoids

Root like structures that help in anchoring

Antheridia

Sperm producing gametophyte

Archegonia

Egg producing gametophyte

Bryophyte life cycle important points

• requires water

• Dominant gametophyte

• Flagellated sperm that swims to egg

• Sporophyte retained on gametophyte

• Haploid spores

• Multiple buds and gametophytes (gamete amplification)

Why did plants evolve beyond bryophytes?

To grow higher! Lignified stems. Vascular tissue needed

Microphylls

Vascular offshoot of main stems. Early leaves

• only in lycophytes

• Represent modification of stems

Megaphylls

broader leaf with multiple veins

In all other vascular plants

Bigger SA!