Patterns of Evolution Flashcards
What is the physical evidence for evolution?
- Homologous characters between different species
- embryological similarities between species
- vestigial characters (Ex. tailbones on humans)
- convergence of traits between different species
- suboptimal design (we dont have ‘perfect’ features)
- geographic distributions
- intermediate/transitional fossils
What are the two major processes of evolution (that together make a new species)?
- cladogenesis and anagenesis
What is cladogenesis?
- the BRANCHING (splitting) of a lineage into two or more descendant lines
- evolution that results in the splitting of a lineage, into two descendent species
What is anagenesis?
- evolutionary CHANGE of various characteristics in each descendant
- where change results in the descendants having different traits from the ancestors
- evolution within a lineage, does not result in a change in number of species
What is pseudoextinction?
a phenomenon in which a taxon changes by anagenesis over evolutionary time, until it is so different from the ancestor that it is reclassified as a new taxon
- no more of the original lineage is present, all have ‘evolved’ into a new species
Most features of organisms have been modified from ________________ __________. _____ _______ are RARE.
Most features of organisms have been modified from PRE-EXISTING FEATURES. NEW CHANGES (de novo features) are RARE.
What is mosaic evolution?
- where different phenotypic characters evolve at different rates.
- species differ in some features but not others
What is allometric growth?
- differential rate of growth of different parts of an organism during its ontogeny
- ex. tall people have larger feet
What is the original heterochrony concept?
- concept introduced by Haeckel in the 1800s
- thought that development stages would recapitulate adult evolutionary stages
- ex. if you had a fish ancestor, you would have an embryonic stage similar to a fish
- this is false
Why is the concept of heterochrony by Haeckel false?
- no recapitulation, an embryos development is increasingly diverse
- we retain commonalities from our ancestors because we have a shared lineage
How do we think of Heterochrony now?
- change in the relative times of developmental events in one species relative to an ancestral species
- in its most basic terms, it is a CHANGE IN DEVELOPMENTAL TIMING
- turning “on” and “off” genes earlier or later will make developmental/phenotypic differences between species
What is Paedomorphosis? The two ways it can occur?
- type of heterochrony
- conditions in which a larva becomes sexually mature without attaining an adult body form
- the retention of juvenile characteristics while at the adult stage
- occurs either through neoteny or progenesis
What is neoteny?
- a type of paedomorphosis
- where a larvae becomes sexually mature by retardation of somatic development relative to sexual development
- there is a slower somatic growth, which results in an adult with larval characters
What is progenesis?
- a type of paedomorphosis
- where a larvae becomes sexually mature by acceleration of sexual development relative to somatic development
- the cessation of growth at an earlier age
- less common than neoteny
What is peramorphosis?
- a type of heterochrony where features extend development beyond the ancestral state
- organisms LARGER than any ancestors were
What are the types of heterochrony?
- paedomorphosis
- peramorphosis
What is convergence?
- where there is a similarity between two species, that is not inherited from a common ancestor
- nearly identical function achieved independently
What are some examples of convergence?
- Vertebrate vs. cephalopod eye
- plants adapted to live in dry habitats (all have dense spines, small leaves, etc.)
- nectar-feeding birds
What is parallel evolution?
- a form of convergence, where similar developmental modifications evolved independently.
- however, parallel evolution refers to more closely related species. Species that share a most recent common ancestor.
What is evolutionary reversal? An example of this
- the return of a character from an apomorphic state, back to a plesiomorphic/ancestral state
- ex. the loss of wings in many winged insect lineages. The original pleiomorphic state is wingless, then wings were gained, then there was a loss of wings.
What is evolutionary radiation?
- the evolution of phenotypic and ecological diversity within a multiplying lineage
- diversification of species into forms to fill different ecological niches
- rapid increase in speciation
What is adaptive radiation? examples?
- a rapid increase in the number of species with a common ancestor, characterized by great ecological and morphological diversity.
- The driving force behind it is the adaptation of organisms to new ecological contexts.
- Darwin’s Galapagos finches, Hawaiian honeycreepers, Hawaiian fruitflies
What is a ‘species flock’
- a group of closely related species all living in the same ecosystem
- evolved within the same ecosystem from a single ancestral species, by repeated speciation events
