Lecture 7: Animal Evolution continued Flashcards
What are the 3 distinguishing characteristics of animals?
- animals are multicellular organisms
- Animals have tissues and organ systems
- Animals are the only kingdom of species that have nervous systems
What is the ancestor of animals? What are animal’s closest living relatives?
What are the 3 lines of evidence supporting the ancestral hypothesis?
The ancestor of animals were a suspension feeding, colonial PROTIST similar to the living CHOANOFLAGELLATES.
- Genes found in animals are only found in choanoflagellates, but no other protist group.
- There are morphological similarities in the collar cells of phyla porifera (sponges) and choanoflagellates
- Collar cells have been found in other animal groups, but not in fungi, plants, or other protists
Define bilateral symmetry
Mirror images of the body are formed by slicing ONE plane through the middle of the animal. Bilaterally symmetrical animals have: - left and right sides - Dorsal (top/back) - Ventral (bottom/front) - Posterior (tail) - Anterior (head)
Describe the nervous system. Do other kingdoms of organisms have these?
The nervous system of an animal uses nerve impulses and muscles to move by coordinating different body parts
Only animals have a nervous system.
When do the earliest animal fossils date?
Approximately 656-550 million years ago.
Define diploblastic and identify the germ layers that will give rise to which tissue systems?
Diploblastic animals have TWO germ layers: Endoderm and Ectoderm that will give rise to the lining of the digestive cavity and most internal organs; the central nervous system
How many identified living species of animals are there? How many do they estimate are still unknown?
1.3 million living species identified
Estimates approaching 8 million are yet unidentified
What are the two major informal groups of animals? which group contains the vast majority of animal species?
Invertebrates (no backbone)
Vertebrates (backbone)
The vast majority of animal species are invertebrates
What are the 5 different body plans of animals?
- Body symmetry: radial or bilateral
- Tissue origin: Diploblastic or triploblastic
- Digestive cavity: alimentary canal or gastrovascular cavity
- Body cavity: coelom, pseudo-coelom, or no coelom
- Skeleton: endoskeleton, exoskeleton, or hydrastatic skeletion
What are the 5 different body plans of animals?
- Body symmetry: radial or bilateral
- Tissue origin: Diploblastic or triploblastic
- Digestive cavity: alimentary canal or gastrovascular cavity
- Body cavity: coelom, pseudo-coelom, or no coelom
- Skeleton: endoskeleton, exoskeleton, or hydrastatic skeletion
Define radial symmetry
Mirror images can be formed by slicing across more than one plane of the animal’s body. Radially symmetrical animals have no distinct right or left sides.
How does body symmetry (structure) relate to an animals lifestyle (function)?
Radially symmetrical animals are generally sessile or planktonic or weak swimmers.
whereas, bilaterally symmetrical species generally have a central nervous system that allows them to coordinate complex movements to fit their motile lifestyle. They also usually have sensory equipment concentrated in the anterior end (head).
T or F: All animals produce true tissues? Why/why not?
FALSE. Sponges do not
Describe the 3 different germ layers that animals can have?
- ENDODERM layer: the innermost layer that will become the lining of the digestive cavity and most internal organs
- SOME animals can form the MESODERM layer: a layer that will form between the endo- and ectoderm layer that will eventually become muscles, blood, and bones
- ECTODERM: the outer body layer that will become the central nervous system
Define germ layer
Embryonic layers of cells that form during development to eventually form different tissues in the adult organism
Define germ layer
Embryonic layers of cells that form during development to eventually form different tissues in the adult organism
Define triploblastic and identify the germ layers and which tissues they will give rise to?
Triploblastic animals contain all three germ layers (endo-, ecto, and mesoderm).
Endo: digestive cavity lining and most organs
Ectoderm: central nervous system
Mesoderm: blood, bones, muscles
What are the two kinds of digestive cavities found in animals?
- gastrovascular cavity
2. alimentary canal
Define gastrovascular cavity
A central cavity with a single opening that functions in digestion and distribution of nutrients.
Food enters and waste exits through the same opening
Define alimentary canal
A complete digestive tract including an opening where food enters at the mouth and a second opening where waste exits through the anus
Define coelom. Do triploblastics, diploblastics, or both have these?
A coelom is the fluid-filled body cavity (space) between the digestive cavity and the body wall where most internal organs are located to cushion organs and allow them to move independently from the body wall. The fluid provides resistance for muscle contractions in animals that don’t have hard skeletons.
Only triploblastic animals have coeloms, but not all of them.
What are the two kinds of triploblastic animals with body cavities? describe them and their tissue origins.
- Coelomates: the body cavity is formed from the tissue derived from the mesoderm
- Pseudocoelomates: the body cavity is formed from tissue derived from both the MESODERM and the ENDODERM.
What is the name for a triploblastic animal with no body cavity? What do they contain instead?
Acoelomates have a solid layer of MESODERM derived tissue that forms between the digestive tract and outer body covering
Describe the 3 kinds of skeletons animals can have. Give an example of an animal for each.
- Exoskeleton: a rigid external support structure
ex. Snail shells - Endoskeleton: A rigid internal support structure
ex. Humans, sea urchins - Hydrostatic skeleton: A flexible support provided by fluid under pressure in a body compartment
ex. earthworms
