PHY - Phylogeny and Origins of Life [OVERVIEW]
Phylogeny and Origins of Life
Introduction
From the tiny ant to the mighty antelope, all species are connected to each other. This module will also tie together some of the themes of previous modules, such as evolution and molecular genetics.
A unifying theme of biology is that all life is related throughout evolutionary time. In this module, we will look at the definition of a species, the causes of speciation, patterns of evolution, building phylogenetic trees from information showing relatedness of species, and the current hypotheses for how life came to be on Earth.
List of Lessons
In this module, we will study the following topics:
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- Speciation – this lesson will discuss both pre-zygotic and post-zygotic barriers for populations that lead to the formation of species.
- Phylogeny – this lesson focuses on cladistics and building trees of life by looking at similarities between species.
- Extinction – this lesson describes the causes and the impact that extinction events have on the diversity of life.
- Origins of Life – this lesson focuses on the scientific evidence that provides support for the spontaneous generation of life on Earth.
Module Objectives
By the end of this module, students will be able to:
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- Describe the types of evidence that can be used to infer an evolutionary relationship.
- Explain how a phylogenetic tree and/or cladogram can be used to infer evolutionary relatedness.
- Describe the conditions under which new species may arise.
- Describe the rate of evolution and speciation under different ecological conditions.
- Explain the processes and mechanisms that drive speciation.
- Describe factors that lead to the extinction of a population.
- Explain how the risk of extinction is affected by changes in the environment.
- Explain species diversity in an ecosystem as a function of speciation and extinction rates.
- Explain how extinction can make new environments available for adaptive radiation.
- Explain how the genetic diversity of a species or population affects its ability to withstand environmental pressures.
- Explain how evolution is an ongoing process in all living organisms.
- Describe the scientific evidence that provides support for models of the origin of life on Earth.
Key Terms
Adaptive radiation - when a single species or a small group of species evolve into several different forms that live in different ways.
Allopatric speciation - when gene flow is interrupted and a population is divided into geographically isolated subgroups.
Behavioral adaptations - inherited traits that help an organism survive and reproduce in a given environment or responses to the environment.
Behavioral isolation - differences in courtship and mating rituals prevent mating.
Coevolution - process whereby 2 species evolve in response to each other over time.
Convergent evolution - process whereby unrelated organisms come to resemble one another because they live in similar environments.
Endosymbiosis - the model that suggests that mitochondria and plastids were once small prokaryotes that began living within larger host cells.
Gametic isolation - sperm and egg are incompatible and no fertilization can occur.
Gradualism ‐ theory that evolution occurred slowly and steadily over time.
Habitat isolation - the physical barriers of the environment prevent mating.
Hybrid breakdown ‐ hybrid adults are feeble or do not survive.
Macroevolution ‐ large scale evolutionary changes that take place over long periods of time.
Mass extinctions ‐ huge numbers of species disappear over a relatively short period of time.
Mechanical isolation - reproductive structures are incompatible and prevent fertilization.
Postzygotic barriers ‐ occur after the egg is successfully fertilized and has developed into a zygote.
Prezygotic barriers ‐ impede reproduction by preventing male and female sex cells from uniting based on physical or behavioral factors.
Protobionts ‐ large organic molecules formed which acted like pre-cells.
Punctuated equilibrium ‐ theory which proposes that sexually reproducing species will experience little evolutionary change for most of their geological history, remaining in an extended state called stasis.
Reduced hybrid fertility ‐ hybrid adults are sterile or infertile.
Reduced hybrid viability ‐ hybrid embryos do not develop correctly.
Speciation ‐ the evolution of a new species that occurs when two similar reproducing beings evolve to become too dissimilar to share genetic information or produce viable offspring.
Species ‐ a group of organisms whose traits are so similar that they can successfully mate with each other and produce viable, fertile offspring.
Sympatric speciation ‐ if gene flow is reduced by polyploidy, habitat differentiation, or sexual selection.
Temporal isolation - different times of the year/seasons prevent mating.
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