Lesson 2 - Concepts, Premises and Pioneers Flashcards
Types of symmetry in animals
- Spherical Symmetry
- Radial Symmetry
- Bilateral Symmetry
the body of the individual can be divided into similar halves by any plane passing through the center
Spherical Symmetry
Symmetry in Amoeba
asymmetry
Symmetry in Volvox
spherical symmetry
Symmetry in Sea jellies
radial symmetry
Symmetry in Spider
bilateral symmetry
example of animals with spherical symmetry
- Volvox
- some sponges
- some corals
- the body of the individual divided into equal halves by any plane passing through the center from top to bottom
Radial Symmetry
example of animals with radial symmetry
- Sponges (Sycon)
- Cnidarians (Hydra, Jelly)
- Echinoderms (Sea Star)
when the body can be divided into two smaller halves by one or two vertical planes only, the radial symmetry is called what?
biradial symmetry
example of animal with biradial symmetry
sea anemones
- body can be divided into two equal halves by a single plane only because the important body organs are paired and occur on the two sides of a central axis
- found in many invertebrates and all vertebrates
bilateral symmetry
segmentation of body into somites or metameres
metamerism
metamerism is the segmentation of body in __ or __
- somites
- metameres
- occurs in cestodes in which every segment is independent of the other and contains complete set of organs that have no connection with other organs in other segments
- during growth new segments are added in front, in the neck region and hence the posterior-most body segment is the oldest one and the anterior segments are younger
Pseudometamerism
where does pseudometamerism occur
cestodes
where are new segments in pseudometamerism added
neck-region (anterior segments are younger)
- serial repetition of homologous organs in each segment but these organs function in coordination with the others
- all segments are integrated into a single functional unit
true metamerism
in true metamerism, all segments are integrate into a __ __ __
single functional unit
ex. of organs in true metamerism
- nephridia
- nerves
- muscles
- reproductive organs
- appendages
an invertebrate organ, found in pairs and performing a function similar to the vertebrate kidneys
nephridium (plural nephridia)
where are new segments in true metamerism added
in front of last segment
- last segment
- terminal part or hind segment of the body in certain invertebrates
pygidium
unsegmented preoral part of the body of a segmented anima
acron
Metamerism is always confined to the intermediate (trunk) segments except the __ __ and a __ __ or telson
- anterior acron (head)
- posterior pygidium
last segment in the abdomen, or a terminal appendage to it, in crustaceans, chelicerates, and embryonic insects
telson
various intermediate segments in animals
- metameres or
- somites
what do animals with true metamerism typically have
- anterior acorn
- posterior pygidium
- metameres or somites
in higher invertebrates, what did metamerism provide
- specialization of segments
- serially repeated organs
specialization of segments in higher invertebrates
- head
- thorax
- abdomen
- evolutionary trend toward concentrating nervous tissue, the mouth, and sense organs toward the front end of an animal
- sense organs or tissues are concentrated on or near the head, which is at the front of the animal as it moves forward
- development of complex neural system and intelligence, clustering of senses to help an animal rapdily sense food and threats
cephalization
what do fully cephalized organisms have
head and brain
what do less cephalized animals display
one or more regions of nervous tissue
what is cephalization associated with
- bilateral symmetry
- movement with head facing forward
what is developed with cephalization
- complex neural system and intelligence
- rapid sense of food and threat
- superior analysis of food sources
cephalization and the senses
- touch
- smell
- eyesight
- hearing
- taste
electroreceptors in sharks for locating prey
Ampullae of Lorenzini
Different Patterns and Processes
- Homology and Homoplasy
- Serial Homology
- Analogy
manifestation of homologous structures in different species
homology
- structures that had beed inherited from a common ancestor
- may be similar or broadly dissimilar morphologically and functionally
homologous structures
homologue is “the same organ in different animals under every variety of form and function”
Boyden (1943)
structures in two different animals are homologous if they come from the same ebryonic precursor
comparative embryology
__ between the structure’s distribution and the hypothesis of relationship for the taxa processing the structure
congruence
structures in two different animals are homologous if they come from the same __ __
embryonic precursor
- presence in different species of structures that look alike but are not similar due to common ancestry
- can result from convergence or accident
homoplasy
evolution of similar structures in unrelated taxa as a result of mutations that are adaptive to similar environments
evolutionary convergence
- similarities in repetitive or serial structures within the same organism.
- semgentally equivalent structure within the organism
- vertebral column, limbs, hands
serial homology
serial homology was originally called as __
homotypy
who termed homotypy
Ernst H. Haeckel
example of serial homology
- vertebral column
- limbs
- hands
- coincidental resemblance
- two structures that have the same function
analogy
example of analogous structures
horns of cattle and rhinoceros
- said that analogy and homology are not mutually exclusive
- comparative anatomist of the 19th century
Richard Owen
Richard Owen: homologous structures that share a similar function
analogous homologue
Richard Owen: nonhomologous structures that share a similar function
analogous homoplasies
Different types of Adaptation
- Biological adaptation
- Preadaptation
- refer to traits shaped by natural selection for their present use
- hereditary modification of a phenotype that increases the probability of survival
- result of environmental pressures that, by natural selection, propagate genetic mutations that have survival value
biological adaptation
- denote traits that initially served different functions but later provided a foundation for new adaptations
- traits that have enables a phenotype to meet a new environmental change before it materializes
- increases the chances of survival in an existing environment
preadaptation
formation of a new species preceded by geographical isolation of a populationi from other populations of the same species
speciation
- evolution of similar structures in unrelated taxa as a result of mutations that are adaptive to similar environment
- produces look-alike features that are not result of inheritance from common ancestor
evolutionary convergence
- developmental history of an individual
- occupies a single lifeline
- begins with embryogenesis, includes postembryonic changes attributable to aging and ends in death
- primary operants are the genes
ontogeny (ontogenesis)
ontogeny occupies a __ __
single lifeline
where does ontogeny begin and end
begins: embryogenesis
end: death
what changes are included in ontogeny
postembryonic changes attributable to aging
primary operants of ontogeny
genes
- evolutionary history of a taxon
- relates a taxon to another taxa in the evolutionary line
- operant is speciation
- requires thousands to millions of years
phylogeny (phylogenesis)
related group of organisms that constitute a taxonomic unit such as family, order, or class
taxon
operant of phylogeny
speciation
features that develop earliest in ontogeny are the oldest phylogenetically, having been inherited from early common ancestors, and features that develop later in ontogeny are of more recent phylogenetic origin
von Baer’s Law
- change to the timing or rate of development relative to the ancestor
- can be the results of relatively small genetic changes that may not even be alterations in DNA sequence, but in the timing of particular genes being expressed during development
Heterochrony
Two forms of heterochrony
- peramorphosis
- paedomorphosis
example of species that show heterochrony
Salamander species: Ambystoma talpoideum
delay metamorphosis of the skull
Any outcome arising from evolutionary changes in developmental rates that involves the addition of new stages to the end of the ancestral development sequence
peramorphosis
- Having some features of the ancestral juvenile stage, but being an adult (with a mature reproductive system
- any evolutionary change in the development of an organism that generates an adult with a “child’s form.”
paedomorphosis
meaning of heterochrony
hetero = other
chronos = time
meaning of peramorphosis
beyond-shape
meaning of paedomorphosis
paed = juvenile
morph = form
example of paedomorphosis
newts and salamanders
- reach sexual maturity without losing gills
discipline and practice of ordering organsims into hierarchies that reflect their morphological similarities and phylogenetic history
systematics
organisms were placed in groups based on both an overall similarity and the possession of unique features
Pre-Darwinian
arrange organisms in historical entities (group based on a common ancestor and all its descendants)
phylogenetic systematics
- process and rules by which we apply names to the groups determined in a systematic analysis
- international code provides the rules of binomial nomenclature
taxonomy
naming in taxonomy
binomial nomenclature
uses a system of hierarchical groupings
Linnaean taxonomy
what forms the binomial system
Genus and species
