origin and diversity of life (PP20) Flashcards
The first part on life was hetero or auto trophic and what does that mean?
The first life on earth was probably heterotrophic
i.e. Used organic carbon for energy
Why is it unlikely that autotrophs were the first organisms
Because Photosynthesis is complicated & requires fairly complex machinery
So autotrophs were probably not the first thing to come about
and Breaking down external sources is a much easier of gaining energy
e.g. Biomolecules from chance electrical events (such as in the Miller and Urey experiment)
Did earliest types of photosynthesis produce oxygen?
If no, did it eventually aCCUMULATE?
no
yes. Oxygen began to accumulate in the atmosphere to a significant degree ~2.7 billion years ago
One benefit of early oxygen.
One disadvantage of early oxygen
-Offered up new opportunities & provided selective pressure (eukaryotes may have had an advantage)
–Oxygen posed a challenge for life (toxic to obligate anaerobes)
explain theory of endosymbiosis
Theory: mitochondria & plastids were formerly small prokaryotes living in larger host cells
Chloroplasts resemble cyanobacteria (photosynthetic bacteria)
Prokaryotic ancestors probably entered host cell as undigested prey or internal parasites
Became more interdependent; host & endosymbionts became a single organism
were first eukaryotes multicellular or unicellular
unicellular
explain what it means when we say “First multicellular organisms were colonies”
it means they were Collections of autonomously replicating cells
What did the specializing of cells for different functions lead to?
Specialization enabled emergence of more complex multicellular organisms
e.g. Animals
what 4 common features does every animal have
1) Multicellularity
2) Heterotrophy
3) Lack of rigid cell walls
4) Motility throughout at least some portion of their life
What are the 3 general features of morphology/development can animals be characterized by
-Body symmetry (or lack thereof)
Asymmetry vs. Radial Symmetry vs. Bilateral Symmetry
-Tissue organization
Acoelomate vs. Pseudocoelom vs. Coelom
-Developmental strategies
Protostomes vs. Deuterostomes
what are the 3 types of symmetry and give an example of an organism that has that.
Bilateral symmetry (1 plain of symmetry) ex:beetle
Radial symmetry (multiple plains of symmetry) ex:starfish
Asymmetry (no symmetry)
ex: sponge
explain bilateral symmtetry
Bilateral animals have a left side & right side: only 1 imaginary cut divides the animal into mirror-image halves
Anterior (head), posterior (rear), dorsal (back), ventral (‘stomach’)
e.g. Lobster (phylum Arthropoda
explain radial symmetry
Parts of a radial animal radiate from the center: any imaginary slice through the central axis divides the animal into mirror images
e.g. Sea anemone (phylum Cnidaria)
what are tissues
Tissues = collections of specialized cells isolated from other tissues by membranous layers
What are the 3 germ layers(embryonic tissues)
ectoderm, endoderm, & mesoderm
diploblasts have two many germ layers? and which tissues does it entail
2
Ecto and Endo derm
explain triploblasts
all 3 germ layers present
Body cavity may or may not be present
explain endoderm
after several cell divisions, cells differentiate into endoderm (inner layer)
Endoderm gives rise to digestive tract
explain ectoderm
ectoderm (outer layer),
Ectoderm gives rise to skin & neural system
explain mesoderm
mesoderm (intermediate layer)
Mesoderm gives rise to muscles & skeleton
DIAGRAM OF CROSS SECTION FOR DIPLE AND TRIPLO AND COELEM
DIAGRAM IN NOTES
What are the 2 tissue organization and explain them
Pseudocoelom: body cavity derived from the blastocoel (only partially lined by mesoderm)
Coelom: body cavity derived from the mesoderm
DIAGRAM IN NOTES
WHAT IS a blastopore
Blastopore: opening of the central cavity in early embryo
if your blastopore becomes a mouth you are…
Protostome:
if your blastopore becomes the anus you are…
Deuterostome:
MEMORIZE TABLE OR PROTO VS DEUTERO
IN NOTES
explain segmentation and its importance
Allows for differentiation of different tissues
Important for locomotion, reproductive structures, nervous system
includes Metameres
Genes repeated for each segment: probably more economical & less error prone than 1 giant set of genes for whole body.
Evolved separately in different phyla
what is a metemere
Metameres = repeating units which forms the animals body
explain cephalization
Formation of an area with large concentration of nervous tissue
In some animals, this appears as a brain
Certain animals have cephalization without a specific brain area
CHECK NOTES FOR PHYLOGENETIC TREES
NOTES
what does the Sub-Kingdom Parazoa include
Includes phylum Porifera (i.e. sponges)
explain phylum porifera
Most “primitive” animals (i.e. fewest derived characteristics)
- No symmetry
- Limited cell specialization
- Do not have distinct organs
- Do not have nervous or muscular tissue
Sessile (don’t get out much)
Suspension feeders
Hermaphroditic
what does the Sub-Kingdom Eumetazoa include?
everything that is not a sponge
explain phylum cnidaria
- Both sessile & motile forms
- Diploblastic
- Radial symmetry
- No cephalization (since radial)
- No segmentation
- Carnivorous: tentacles armed with cnidocytes – cells with harpoon threads (nematocysts)
what are cnidocytes
cells with harpoon threads (nematocysts)
creatures with radial symmetry are part of what clade?
clade radiata
What is the body plan of cnidarians
Body plan = sac with central digestive compartment (gastrovascular cavity)
Single opening functions as both mouth and anus
what are the 4 classes of cnidarians and examples
Hydrozoa (man of war, hydras),
Scyphozoa (jellies, sea nettles)
, Cubozoa (box jellies, sea wasps),
Anthozoa (sea anemones, corals).
know the difference because poly/hydra and medusa
PICS ON SLIDES
if you have bilateral symmetry you are part of which clade?
clade Bilateria
Explain phylum Platyhelminthes
-Triploblastic
-Acoelomate
No circulatory system
Digestive cavity = single area that uses same opening as mouth & anus
Bilateral symmetry
-Left/right, anterior/posterior, dorsal/vemtral
Cephalization
-Anterior ganglia (simple brain)
-No segmentation
Includes flatworms, flukes, tape worms
explain phylum nematoda
- Triploblastic
- Pseudocoelomate
-Crude circulatory system
Digestive cavity has 2 ends (anterior & posterior)
- Bilateral symmetry
- Cephalization
No segmentation
Includes roundworms
explain phylum mollusca
- Triploblastic
- Coelomate
- Tissue-covered body cavity
-Bilateral symmetry
Varying levels of nervous tissue development
Some are highly cephalized (octopi, squid, cuttlefish) with large brains & complex sensory machinery (lensed eyes)
-No segmentation
-Not considered to have proper appendages (like arms or legs)
Have muscular regions that can help with movement
Includes snails, slugs, oysters, clams, squids, octopi
explain phylum annelida
Triploblastic
Coelomate
Tissue-covered body cavity
Bilateral symmetry
Cephalization
-Segmented
Repeated regions of the body structure (similar internal components)
Allows for localized specialization of different tissues
Non-jointed appendages Small legs (cetae) help with the movement Includes earthworms, sandworms, leeches
explain phylum anthropda
triploblastic
-Coelomate
Open circulatory system
Bilateral symmetry
-Cephalization
More complex sensory apparatuses (compound eyes, olfaction)
-Segmented
Localized specialization of different tissues
Jointed appendages
Specialized for eating, capturing prey, walking, swimming
Exoskeleton derived from cuticle
Includes insects, crustaceans, spiders, scorpions, centipedes
explain phylum echinodermata
Triploblastic Coelomate -Bilateral + radial symmetry (Larvae are bilatera)l Adults show pentaradial symmetry
No cephalization
No segmentation
Deuterostome
(Blastopore develops into the anus)
Many are sessile as adults
Differ from cnidarians by having a fully closed internal cavity, digestive system, nervous tissue.
Includes sea stars, sea cucumbers
explain phylum chordata
Triploblastic Coelomate Bilateral Cephalization (Highly cephalized)
Segmented
Localized specialization of different tissues
Deuterostome
A bunch of novel characteristics: e.g. Notochord
Includes some invertebrates & all vertebrates
which phylums are part of clade radiata?
phylum cnidaria
which phylums are part of clade bilateria
- platyhelimnthes
- annelida
- nematoda
- mollusca
- anthropoda
- echinodermata
- chordata
which phylums are part of prostostomia
- platyhelimnthes
- annelida
- nematoda
- mollusca
- anthropoda
which phylums are part of deuterostomia.
- chordata
- echinodermata
what are the 4 traits that all chordates display at some point in their lives
- Presence of a flexible notochord
- Presence of a hollow dorsal nerve cord
- Presence of pharyngeal slits
- Presence of a muscular post-anal tail
Do all chordates show all traits during their whole life?
no
All chordates share this set of 4 derived characters, ALTHOUGH some species possess some of these traits only during embryonic development
explain the notochord and its function
- Flexible longitudinal rod located between the digestive tube & nerve cord
- Provides structural support
In most vertebrates, a more complex, jointed skeleton develops → adult retains only remnant of embryonic notochord
explain the dorsal hollow nerve chord
Also called a “spinal cord”
Develops from a plate of ectoderm that rolls into a tube dorsal to the notochord
Develops into the central nervous system (CNS = brain & spinal cord)
explain pharyngeal slits
- Allow for movement of gases in aquatic environments & filter-feeding
- Grooves in the pharynx develop into slits that open to the outside of the body
- Develop into parts of the ear, head, & neck in terrestrial vertebrates
explain post anal tail and its function
- Tail extending posterior to the anus
- In many species (e.g. humans) it is lost during embryonic development
- Used for movement / balance
- Provides much of the propelling force in many aquatic species
- Contains skeletal elements & muscles
do all chordates keep their post anal tail?
In many species (e.g. humans) it is lost during embryonic development
what is a craniate?
chordates with heads
what did development of a head lead to for chordates
Development of a head opened up a new way of feeding for chordates: active predation
what common characteristics do craniates share?
Craniates share some common characteristics:
skull, brain, eyes, & other sensory organs
what is a neural crest and where is it found
collection of cells that appears near the dorsal margins of the closing neural tube in an embryo
found in choradates
what do neural crest cells lead to ?
These cells give rise to a variety of structures: e.g. some of the bones & cartilage of the skull
