Evolution and tree of life Flashcards
What are the differences between hypothesis and theories?
A hypothesis is an educated guess, based on observation. It can be supported or refuted through experimentation or more observation. A hypothesis can be disproven but not be proven true. A theory on the other hand summarizes hypothesis though repeated testing. A theory is valid so long as no evidence disputes it. As evidence accumulates, a hypothesis can become accepted as an explanation of a phenomenon. In inter words, a theory Is a hypothesis that we fail repeatedly to disprove.
Why disprove instead of prove hypotheses?
Because a hypothesis stands to be falsifiable, and as surmounting evidence accumulates, it is crucial to move forward and clarify. Hypotheses serve as a guide for future data collection, they cannot be proven correct if null. If confirmed by a large number of empirical tests, and is powerful in explaining a large variety of related phenomena, it obtains theory status.
What is the intellectual framework evolutionary theory aims to provide?
A framework for the present observed life and biodiversity.
What methods do evolutionary scientists use?
- evolutionary scientists use the scientific method to show how evolution worked and is currently working.
- evolutionary scientists use the comparative method rather than just experimentation, and integrate phylogenic systematics, molecular, morphological, paleontological, and a modern synthesis of a wide array of methods and approaches.
What is the thinking in the modern synthesis of evidence for for evolutionary theories?
A 20th century consensus of ideas from several biological specialities which provides a widely accepted account of evolution. Draws from genetics, cytology, morphology, botany, ecology, paleontology, and systematics.
What is Lamarckian theory? How does it differ from our current thinking?
Lamarcks proposed evolutionary mechanism was the inheritance of acquired characteristics. It entailed that organisms, by striving to meet the demands of their environment, acquire adaptations and pass them by heredity to their offspring- I.e. giraffe long neck trait to stretch for food changes accumulated to produce long necked giraffes. Lamarcks theory was transformational in the sense that individual organisms transform their characteristics through the use and disuse of parts, heredity makes corresponding adjustments to produce evolution. It proposed multiple independent origins of species. Darwin’s theory of evolution on the other hand was variational. Evolution occurs at the level of population and includes changes across generations in the organismal characteristics that prevail in the population. Darwin proposed organisms possessing hereditary characteristics that conferred an advantage for survival or reproduction would leave more offspring than would other organisms, causing populations to accumulate across generations the characteristics most favorable to the survival and reproductive success of their bearers. A single common ancestor.
What are the key components of Darwin’s evolutionary theory?
The key components of Darwin’s evolutionary theories include:
- perpetual change
- multiplication of species
- gradualism
- common descent
- natural selection
What does perpetual change imply? Give an example from Kansas?
Life is not static or constant over time.
- extensive fossil record
- constantly changing lifeforms over human history
- lifeforms changing over human lifetime
-life is NOT cycling between 2 or several states.
- life forms constantly changing in response to the environment or face extinction
- what is today isnt necessarily tomorrow
> Kansas: Cretaceous= mosasaurs, toothed birds,
Pleistocene= saber tooth cat, giant ground sloth, mammoth
What does common ancestry imply?
Common descent assumes all organisms descended from a single common ancestor. Until Darwin others assumed independent origins recognizing the relationships between species.
- common descent predicts a tree like structural relationship between organisms.
- you can trace the ancestor of all present organisms back and infer their phylogenic relationship through homology.
- Darwin dealt with what happened after the first cell evolved, but did not touch on what the origin actually is.
What does homology imply?
That similar structures in different organisms derived from their common ancestor.
-evidence demonstrates shared characters result from the genes of a common origin= homologous genes
What does gradualism change imply?
Essentially, speciation through the gradual accumulation of small, incremental changes. Gradualism implies large differences in anatomical traits which characterize how different species accumulate in incremental changes over long periods of time. This is important because genetic changes having large effects on organismal form are generally harmful to an organism. Some genetic variants that have large effects on organismal form may be beneficial however, and it does not explain all structural differences between species
How are the concepts of gradual change, common ancestry, and homologous structures related?
All three recognize a common ancestor with different organisms related by a tree like structure with different structures in different organisms derived from their common ancestor, and that incremental anatomical differences distinguishing species generally accrued over a long period.
What does punctuated equilibrium imply?
Rapid, episodic speciation.
Why are the morphology and gene based trees often incongruent?
If this were the case, then some skeletal structures either arose multiple times or were lost on some lineages.
What is reproductive, temporal, behavioral, and geographic isolation?
Speciation that results from the evolution of reproductive barriers between geographically separate populations is geographic or allopatric speciation. Temporal isolation involves, for example, different times of sexual maturity in flowering plants. Reproductive isolation involves for example, a collection of mechanisms, behaviors and processes that prevent the members of two different species from mating or producing offspring. Behavior wise, mating rituals prevent and isolate apparently similar groups.
