T12/T13 - Evolution of animas Flashcards
What are some advantages/disadvantages of switching sexual reproduction to parthogenesis?
Parthogenesis = form of asexual reproduction
Dis;
- less diverse population
- losing some potentially beneficial alleles leading to potential reduction in fitness
- reduces chance for new genetic combinations
Ad;
- does not need a mate
- population does not go extinct
- females do not incur 2-fold cost for reproduction output
- produces female offspring
- eliminates energy spent on finding a mate
- good if there are not enough males
What is an animal?
- Eukaryotes
- Multicellular
- Heterotroph (organic source of carbon to produce its own organic molecules
- Breathes oxygen = aerobic/oxidative respiration
- Able to move
- Able to reproduce sexually (sometimes asexually too)
- Cells organized into tissues
- Development goes through blastula stage
- Absence of cell way - extracellular matrix with interconnected proteins to maintain cohesion and structural support
What is an example off an animal that is not a heterotroph?
Elysia chlorotica - sap sucking slug
- steals chloroplasts (kleptoplast) from algae but are not transmitted to next generation
- allows for some transfer of photosynthetic protein genes into slug’s genome
What are cadherins?
Proteins involved in cell to cell attachment
Animal caherins also contain the cytoplasmic cadherin domain (CCD)
- A highly conserved region not found in the choanoflagellates
What does multicellulairty require?
The evolution cell adherence (attachment) and cell signaling (communication)
How are sponges specialized and different from us?
Sponges have choanocytes and amoebocytes
Choanocytes = resemble choanoflagellates (feeding by filtration)
Amoebocytes = transport nutrients to other cells and can differentiate into any other cell
Why do sponges contrast with Eumetazoa (a branch underneath) ?
Sponges (porifera) do not have true tissues
- cells are not connected together and are not separated from other tissues by membranous layers (epithelial tissue we see in all other animals)
- do not contain neurons
Describe reproduction in animals
- Life cycle is dominated by the diploid phase; diplontic life cycle
- 2 haploid games are produces by meiosis and do not undergo mitosis; unicellular haploid phase (non-motile egg and flagellated sperm)
- all animals reproduce sexually - some can also do asexual
What is an example of asexual reproduction in animals?
Fragmentation in sponges and flatworms (planaria)
- presence of neoblasts; undifferentiated stem cells that can regenerate an entire organism
What is parthogenesis?
Asexual reproduction in which females produce offspring from unfertilized eggs
(zebra shark, ner mexico whiptail…)
What is radial symmetry vs bilateral symmetry?
Radial = central axis, no anterior or posterior
Bilateral = dorsal and ventral sides, anterior region (mouth/sensory organs), posterior region (tail, anus, feeding, locomotion)
What are hox genes? What is their role?
Hox genes = homeotic genes, regulatory genes that control the placement/spatial organization of body parts by controlling the developmental fate of group cells
- gives rise to identity of tissues, orientation, segmentation, repetitions…
Role = development of animal embryos, they control the expression of over 100 other genes to determine morphology
What is a larva?
Sexually immature form of an animal that is morphologically distinct from the adult
- will usually eat different food and live in a different habitat than the adult (less competition)
- tadpoles into adult frogs
What is metamorphosis?
Developmental transformation that turns the animal into a juvenile that resembles an adult but is not yet sexually mature (butterflies)
What is a blastula?
Diploid zygote undergoes mitosis without cell growth
What is gastrulation? What does this form?
The formation of a gastrula through infolding
Formation of embryonic tissues that will develop into adult body parts
- from 1 layer to multilayer structures; cell layers will now have different functions
During the 8-cells stage, what can cell divisions undergo?
Spiral cleavage = oblique to the axis of the body
Radial cleavage = parallel to the axis of the body (cells sitting on top of one another)
Determinate cleavage = each cell defines a specific part of the embryo
Indeterminate cleavage = each cell has the potential to produce a complete embryo (each cell has all the genes to produce any part of the embryo)
Gastrulation (gastrula) = formation of embryonic tissues that will develop into adult body parts
Blastopore = develops into; mouth (protosomes = mouth 1st) or the anus (deuterstomes = mouth 2nd)
What is the archenteron? How does this relate to the blastopore?
Archenteron = primitive gut (external environment)
Blastopore is the opening of the archenteron
What are the 3 embryonic tissues?
Endoderm (inner)
Mesoderm (middle)
Ectoderm (outer)
How do animal with radial vs bilateral symmetry differ in their embryonic tissues?
Radial = Ectoderm and endoderm
- Diploblastic
Bilateral = Ectoderm, mesoderm and endoderm
- Triploblastic
What is the coelom?
The cavity lined by tissues derived from the mesoderm between the digestive tract and outer body layer
- some triploblastic animals lost the coelom (acoelomates)
- organs are suspended in the coelom and become more specialized (more effecient digestion, increased production and storage of gametes)
What are some functions of body cavities?
- Structural support of the body (skeleton/hydrostatic skeleton)
- Transport and diffusion system (nutrients, gas exchanges, waste elimination)
- Allow the growth of organs and their independent movements
What is the notochord?
A dorsal, longitudinal and flexible rod from the mesoderm along the anterior-posterior axis of a chordates
- gives structural support (spine in vertebrates)
What are some factors the surface to volume ratio influences?
- heat conservation
- metabolic activity
- exchanges (nutrients/gases)
As organism gets smaller, S-V ratio decreases, heat loss is decreased for larger organisms, SA is proportionally smaller for larger organisms
What does the source of heat and constancy of the internal env. tell us about an organism?
If the source of heat is internal (metabolism) = endotherm
If the source of heat is external (sunlight) = ectotherm
If there exists a mechanism to attentuate the variations of the interal environment when the external environment flucuates = homeotherm (regulator)
If the variations in the internal environemtn can be tolerated when the external environment fluctuates = poikilotherm (conformer)
What are invertebrates? What kind of group do they form?
Invertebrates = absence of backbone (spine)
Forms a paraphyletic group
What are some features that chordates possess?
Notochord (muscles attach to the notochord for locomotion)
Dorsal nerve chord
Pharyngeal slits behind the mouth (filtration during feeding)
Post-anal tail with a skeleton and muscles
What are the 3 modes/reproduction of internal fertilization of chondirchthyes
- Oviparous; egg laying and external hatching
- Ovoviviparoud; embryo feeds from the egg’s yolk then hatches in the uterus
- Viviparous; embryo feeds from the mother through the placenta and until birth
What are tetrapods?
“Four limbs” with digits
Allowed for new land niches and adaptations leading to colonization of land
What are some adaptations that led to the colonization of land?
- Support of the body against gravity
- Breathing in the air
- Hearing in the air
- Resistance against dry environments
- Vascular system with lungs and organs
What are amniotes?
Air insulation (during embryo stage) and ventilation (thoracic cage)
What are 4 embryonic membranes found in amniotes?
- Chorion = outer membrane (gas exchange)
- Amnion = surrounds the cavity (mechanic protection)
- Allantois = surrounds the disposal sac (metabolic wastes)
- Yolk sac = stock of nutrients
How did the evolution of the amniotic egg lead to the independence of tetrapods from aquatic environmenets?
- Provides air insulation and the embryo does not dry (moist env. in the egg)
- Allows gas exchange, nutrition and metabolic waste disposal (in aquatic env these were done by diffusion with surrounding water)
- Provides mechanical protection
