BIO 2 - Q3 W1

• John Ray

  an English scientist was the first to carry out a thorough study of the natural world. He was the first to establish the modern concept of a species through his work. He noted that organisms of one species can only interbreed among its members, and he used it as the basic unit of taxonomy. He also studied fossils and recognize them as once-living organisms.
• Carolus Linnaeus

  -He developed most influential early classification system

  -In fact, all modern classification systems have their roots in Linnaeus' system. Linnaeus was a Swedish botanist who lived during the 1700s.

  -He is known as the "father of taxonomy." Linnaeus tried to describe and classify the entire known natural world.

  -In 1735, he published his classification system in a work called Systema Naturae ("System of Nature").
• Thomas Malthus

  -was an English economist.

  -He wrote a popular essay called "On Population." He argued that human populations have the potential to grow faster than the resources they need. When populations get too big, disease and famine occur. These calamities control population size by killing off the weakest people.
• Georges Cuvier

  -He developed Catastrophism based on paleontological evidence in the Paris Basin.

  -Cuvier was there when he observed something peculiar about the fossil record. Instead of finding a continuous succession of fossils, Cuvier noticed several gaps where all evidence of life would disappear and then abruptly reappear again after a notable amount of time. Cuvier recognized these gaps in the fossil succession as mass extinction events.
• This led Cuvier to develop a theory called catastrophism. Catastrophism states that natural history has been punctuated by catastrophic events that altered that way life developed and rocks were deposited.
• James Hutton

  -In geology, gradualism is a theory developed by James Hutton according to which profound changes to the Earth

  -This theory inspired an evolution theory in paleontology, also called gradualism, according to which the species appeared by the gradual transformation of ancestral species. According to this theory, the population of a species is transformed slowly and progressively into a new species by the accumulation of micro-evolutionary changes in the genetic heritage.
• Lamarck

  -In his attempt to explain the changes that happen in organisms from one generation to the next, he came up with the law of use and disuse.

  -It states that certain organs of the body that were used extensively to cope with the environment becomes more developed, while organs that were not used deteriorates

  -A famous example of this is the giraffe. According to Lamarck's idea, giraffes developed long necks because they always stretch their necks to reach leaves on high branches. Their necks gradually became longer as a result, and they passed on this trait to the next generation.
• Alfred Russel Wallace

  -was able to come up with the same idea about evolution as Darwin while studying nature and collecting bird and insect specimens in the Malaysian archipelago.
• Modern Synthesis Theory

  The Modern Synthesis Theory is basically a combination of Mendel's rule of inheritance and Charles Darwin's theory of evolution by natural selection, resulting in a unified theory of evolution. Also known as the Neo-Darwinian Theory, it explains the concepts which occur when the allele frequency of a population changes. The formation of a new species can happen if the changes are significant enough.
• Evidence from Structures

  -Structures in different organisms can be compared to infer common lineage. Darwin thought of evolution as "descent with modification," a process in which species change and give rise to new species over many generations.
• Homology

  -If two or more species share a unique physical feature, such as a complex bone structure or a body plan, they may all have inherited this feature from a common ancestor. Physical features shared due to evolutionary history (a common ancestor) are said to be homologous.
• Analogy

  -To make things a little more interesting and complicated, not all physical features that look alike are marks of common ancestry

  -Instead, some physical similarities are analogous: they evolved independently in different organisms because the organisms lived in similar environments or experienced similar selective pressures. This process is called convergent evolution. (To converge means to come together, like two lines meeting at a point.)
• A phylogenetic tree, also known as an evolutionary tree, is a graphical representation that shows the evolutionary history between a set of species or taxa during a specific time. In other words, it’s a branching diagram illustrating the evolutionary relationships among various biological species or entities based on their physical or genetic characteristics.

  
• Vestigial structures

  Vestigial structures that can be found in the human are the appendix, tail bone, sinuses, wisdom teeth, muscle in the external ear, erector pili muscles, tonsils, and the male nipples just to name a few.
• Embryology

  -Embryology is the study of the development of an organism from an embryo to its adult form.

  -Common structures are shared in the embryo stage and disappear by the time the embryo reaches the juvenile or adult form.

  -It is considered to be a form of evidence for evolution and a way to link various species on the phylogenetic tree of life.

  -Embryology is an important cornerstone of studying biological evolution and can be used to help determine the similarities and differences between various species.
• Evidence from Molecular biology

  Like structural homologies, similarities between biological molecules can reflect shared evolutionary ancestry. At the most basic level, all living organisms share:

  
  

  - The same genetic material (DNA)

  - The same, or highly similar, genetic codes

  -The same basic process ofigene expression (transcription and translation)

  - The same molecular building blocks, such as amino acids
• Evidence from Biogeography

  Biogeography is the study of the geographic distribution of plants and animal. It is I concerned not only with habitation patterns but also with the factors responsible for variations in distribution.
• SPECIES

  -is often defined as a group of individuals that actually or potentially interbreed in nature.

  -it is a group of related organisms that share common characteristics and can only produce offspring among themselves. But even among similar species, there are some barriers that may prevent them from interbreeding.
• Pre-zygotic barriers

  These are isolation mechanisms that prevent fertilization and zygote formation.
• Pre-zygotic barriers

  //Ecological isolation//

  -also called geographic or habitat isolation. Species occupy different areas or habitats thus, they never come in contact with one another.
• Pre-zygotic barriers

  //Temporal isolation//

  -different groups may not be reproductively mature at the same season, or month or year.
• Pre-zygotic barriers

  //Behavioral isolation//

  -patterns of courtship are different
• Pre-zygotic barriers

  //Gametic isolation//

  -incompatibilities between egg and sperm prevent fertilization
• Pre-zygotic barriers

  //Mechanical isolation//

  -differences in their reproductive organs prevent interbreeding and thus, prevent the birth of a sterile hybrid.
• Post-zygotic barriers

  -These are isolation mechanisms that allow fertilization but nonviable or weak or sterile hybrids are formed.
• Post-zygotic barriers

  //Hybrid inviability//

  -fertilized egg fails to develop past the early embryonic stages

  -Which reduces a hybrid's capacity to mature into a healthy, fit adult.
• Allopatric speciation or geographic speciation

  (allo - other, patric - place; 'other place')

  -occurs when some members of a population become geographically separated from the other members thereby preventing gene flow. Examples of geographic barriers are bodies of water and mountain ranges.
• Sympatric speciation

  (sym - same, patric - place; 'same place')

  -occurs when members of a population that initially occupy the same habitat within the same range diverge into two or more different species. It involves abrupt genetic changes that quickly lead to the reproductive isolation of a group of individuals. Example is change in chromosome number (polyploidization)
• just review

  
• Parapatric speciation

  (para - beside, patric - place; 'beside each other')

  -occurs when the groups that evolved to be separate species are geographic neighbors. Gene flow occurs but with great distances is reduced. There is also abrupt change in the environment over a geographic border and strong disruptive selection must also happen.