Chapter 27/28 test Flashcards
What present day organism is similar to what animals evolved from?
Single celled eukaryotes present to choanoflagellates
How many species have been discovered and what is the predicted actual number?
1.3 million discovered and actual estimate of 8 million
What are Edicaran Biota?
560 million year old fossils that are members of an early group of soft bodied multicellular eukaryotes
What is the sponges’ status on the phylogenetic tree of animals?
They are said to be basal animals because their lineage originates near to roots of the tree
What are choanocytes? Which cells do they resemble?
aka collar cells, they engulf food bacteria and other particles via phagocytosis. The interior of the body of a sponge is lined with these cells. They resemble choanoflagellates
What are animals thought to have evolved from?
a choanoflagellate-like ancestor
What are amoebocytes?
Mobiles cells used by sponges, named for their use of pseuodpodia. They move around the cell, take up food from water and choanocytes, digest it and carry nutrients to other cells
What is the basic morphology of a cnidarian?
A sac with a central digestive compartment/gastrovascular cavity with a single opening
What are feeding characteristics of cnidarians?
They are carnivores that often used tentacles situated in a ring around their mouth to capture and pass food through the gastrovascular cavity. Enzymes secreted into the cavity turn the food into a nutrient rich broth and cells lining the cavity absorb nutrients and waste is expelled
Describe the neural systems of cnidarians.
The have very simple forms of nerves/muscles. Movement is coordinated by a noncentralized nerve net distributed throughout the body. They have no brain and can detect and respond to stimuli from all directions
What are bilaterians?
Most of the fossils from the Cambrian explosion, bilaterians are an enormous clade whose members have a complete digestive tract and a two-sided, bilaterally symmetric form
What types of fossils emerged during the cambrian explosion?
fossils with hard tissue that hunted prey
Why are hypotheses as to why diversity of Ediacaran life forms decrease during the cambrian explosion?
Natural selection led to a decrease of these organisms, an increase in atmospheric oxygen, and the appearance of Hox genes and other genetic changes affecting the regulation of developmental genes facilitated the evolution of new body forms
What is radial symmetry?
Are symmetrical when sliced through the center with a straight line
What do dorsal and ventral mean?
Dorsal: Top
Ventral: Bottom
What are neural characteristics of animals with a bilateral symmetry plan?
Many of them have sensory equipment in the anterior end and a central nervous system/brain in the head
How mobile or radial animals compared to bilateral animals?
Radial: Live attached to something or drift/weakly swim
Bilateral: Move actively from place to place
What are the ectoderm and endoderm? Where are they present?
Ectoderm: the germ layer covering the outer surface of the embryo, gives rise to the outer covering of the animal, and for some animals, the central nervous system
Endoderm: inner most germ layer, gives rise to the lining of the digestive tract and organs such as lungs and livers of vertebrates
Present in all animals with true tissues
What is the mesoderm? where is it present?
All bilateral animals have a mesoderm. It is a third germ layer that fills much of the space between the ectoderm and endoderm, forming the muscle and most other organs between the digestive tract and outer covering of the animal
What is a body cavity?
a fluid or air filled space located between the digestive tract and outer wall. It has fluid cushions that suspend organs to prevent internal injury, it contains noncompressible fluid that acts as a skeleton against which muscles can work in soft bodied animals, and it enables internal organs to grow and move independently of the outer body wall
What allows us to study evolutionary relationships among living animals?
rRNA, Hox genes, protein coding nuclear genes, mitochondrial genes and morphological traits
What is eumetozoa? What are basal eumetazoa like?
A clade of animals with true tissues, containing all animals except sponges and a few others. Basal eumetazoans have 2 germ layers and radial symmetry
What is bilateria?
A clade containing most animal phyla. Defined by bilateral symmetry and 3 germ layers. Their rapid diversification occurred during the cambrian explosions
What is the biggest of the phyla on earth?
Arthropods
Why have arthropods been successful?
Their segmented body, exoskeleton, and jointed appendages
How did arthropods change as they evolved?
They went from having little variation in body segments to having a more efficient body plan and having more variety among separate segments
What do scientists think drove the evolution of arthropods?
Changes in sequence or regulation of Hox genes
What phylum do vertebrates belong to?
Chordata
What body plan do chordates have?
bilateral
What are the 4 key characteristics of chordates?
- A dorsal, hollow nerve chord: unique structure that develops into the brain/spinal chord
- Pharyngeal slits/clefts: structures in adults the function in filter feeding in gills or the head
- Notochord: flexible rod providing skeletal support
- Post anal tail: Muscular post anal tail
What do other animals have instead of a dorsal, hollow nerve chord?
A ventral, solid nerve chord
What major evolutionary step came after the main body plan in chordates?
Vertebrates with a well defined head with a skull, eyes, brain and other sensory organs
What were vertebrates mor efficient at than their ancestors?
Capturing food and avoiding being eaten
What are gnathostomes? Why did they succeed?
Jawed vertebrates. They succeeded because their paired fins and tail allowed them to swim well, their jaws allowed them to grab and bite prey
What are chondrichthyans?
A clade including sharks, rays and their relatives. They are some of the biggest and most successful vertebrate predators in the ocean. They have a skeleton composed mostly of cartilage(name means cartilage fish)
What are osteichthyes and their main lineages?
A clade consisting of the vast majority of vertebrates. The typically have a bonu endoskeleton, lungs or lung derivatives. Most of them have bony rays that support their fins. There are also vertebrates in this clade with lobe fins, fins with rod shaped bones surrounded by a thick layer of muscle in their fins
What are tetrapods?
Vertebrates with limbs and digits
Which group first colonized land according to fossil evidence?
Arthropods
What is the ancestor of land plants?
Green algea
What is a cuticle?
The covering of the body of an arthropod, an exoskeleton made of layer and protein and chitin. It can thick and hard or thin and flexible
What diversified insects?
Increased diversity in plants