BIO Flashcards
- A system used by scientists to describe timing and relationships in Earth’s history
- Covers from the formation of the planet (4.6B years ago) until today
Geologic Time Scale
Largest interval of the geologic time scale
Eons
4 sub eons
Hadean, Archean, Proterozoic, Phanerozoic
- Formation to 4B years ago
- Intense volcanic activity and frequent meteor attacks
- Cooling and solidifying of the Earth’s crust
- No life known yet
Hadean
- 4 to 2.5B years ago
- Time of early life on Earth and micro organisms started to appear
- First eukaryotes, single celled Algae (1.4B years ago)
- Anaerobic prokaryotes-bacteria and archeans (3.5B years ago)
- Oxygen levels rised due to photosynthetic organisms
Archean
- 2.5B to 541M years ago
- Time of evolution of early life forms and formation of continents
- Appearance of multi-celled organisms
- Eg. Sponges, colonial algae and soft-bodied invertebrates
Proterozoic
- 541M years to present
- Evolution of multicellular life forms and development of first animals
- Includes Paleozoic, Mesozoic and Cenozoic
Phanerozoic
3 eras
Paleozoic, Mesozoic and Cenozoic
Period that spans from tens to hundreds of millions of years
Era
- 541M to 252M years ago
- Rise of the first fish and the land plants
- Time of great diversification
- Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian
Paleozoic
- 252M to 66M years ago
- Meaning middle life
- Time of the dinosaurs
- Triassic, Jurassic, Cretaceous
Mesozoic
- 66M years ago to present
- Evolution of modern mammals and rise of humans
- Paleogene, Neogene, Quaternary
Cenozoic
Spans no more than one hundred million years
Periods
- Smallest division of the geologic time scale
- Characterized by distinctive organisms
Epoch
Lasted from about 66m to 56m years ago
Paleocene Epoch
- 55.8M to 38.9M years ago
- Oldest known fossils of the modern mammals appear here and they were all small weighing less than 10kg
Eocene Epoch
- 33.9M to 23M years ago
- Appearance of the first elephants with trunks, early horses and grasses
Oligocene Epoch
- 23.03M to 5M years ago
- Warmer global climates
- First appearance of Kelp Forests and Grasslands
- Expansion of grasslands is correlated to drying of continental interiors
Miocene Epoch
- 5.3M to 2.6M years ago
- Time of global cooling
- Cooling and drying of the global environment lead to the enormous spread of grasslands and savannas
- Major change in vegetation
- Rise of long legged grazers
Pliocene Epoch
- 2.6m to 11,700 years ago
- Extremely close to modern ones
- Species of Pleistocenes conifers, mosses, flowering plants, insects, mollusks, birds, mammals and others survive up to this day
Pleistocene Epoch
- 11,700 to present day
- The time since the last major glacial epoch or “ice age”
- Small-scale climate shifts
- Little Ice Age - 1200 and 1700 A.D
- Age of Humans
Holocene Epoch
is the gradual process of change that transformed life on Earth. It refers to descent with modification.
Evolution
- process through which population of living organisms adapts and change
- The Struggle for Existence-members of each species have to compete for food, shelter, other life necessities Survival of the Fittest-Some individuals better suited for the environment
Natural selection
nature provides the variation among different organisms, and humans select those variations they find useful.
Artificial Selection
- genes or damaged or changed which alters the DNA sequence.
- It is the driving force of evolution that is a random change in an organism’s genetic makeup so it changes the nature of the DNA in one or more chromosomes that cause the rise of new alleles which causes them to become the source of genetic variation in the population.
Mutation
which is a mutation which is beneficial to the population
Positive mutation
which reduce the chance of survival of the species or organisms
Negative mutation
this mutation doesn’t change the chance of survival of an individual
Neutral mutation
mechanism of evolution that may occur during migration or individuals from one group that’s going to transfer to another and when that migrating individual interbreed with the new population they will contribute their genes to the gene pool of the local population. The keyword for gene flow is migration and geographic isolation.
Gene flow
It is the frequency of a trait that changes by chance randomly. It refers to the random change in the frequency of a gene. It occurs to some degree in populations of finite size. In genetic drift we can see two examples:
Genetic drift
refers to the sharp production in size of the population due to environmental changes such as calamities like flood earthquakes, fires, droughts and even diseases or human activities such as widespread violence.
Population bottleneck
it is another extreme example of drift which occurs when a small group of individuals break off from a larger population to establish a new colony. This new colony is being isolated from the original population and those founding individuals may not represent the full genetic diversity of the original population. This can cause some alleles that can be missing altogether. This founder effect is similar in concept to the bottleneck effect but it occurs via different mechanisms. It happens due to colonization rather than catastrophe which we can see in the bottleneck effect.
Founder effect
It is the classification comprising organisms that share common characteristics and are capable of interbreeding.
Species
- Process used by natural selection
- As traits are passed through generations, there is modifications
- Natural Selection will either get rid of the modifications or increase it based on the environment
Descent with Modification
Species of sexual organisms are defined by reproductive Isolation
Reproductive Isolating Mechanisms
Prevents Fertilization and Zygote formation
Prezygotic Isolation Mechanism
Allows fertilization but Nonviable/weak/sterile hybrids are formed
Postzygotic Isolation Mechanism
- One original ancestral species forms 2 or more new descendant species
- Must have evolved from one original species population making it impossible to interbreed
Speciation
- Also known as Geographic Speciation
- Groups from an ancestral population evolve into different species due to a period of geographical separation
- Variation will affect their traits and reproduction making it impossible to interbreed
Allopatric Speciation
- Same ancestral speciation but evolve still without any geographic separation
- Happens when there are no physical barriers blocking species from mating with one another, but all members are near each other
Sympatric Speciation
- Occurs when a smaller population is isolated, usually at the periphery of a larger group
- They become differentiated enough to be identified as new species
- Think of racism
Parapatric Speciation
- First scientist to attempt to explain the evolutionary process
- “Organisms altered their behavior in response to environmental change”
- “Their changed behavior, in turn, modified their organs, and their offspring inherited those improved structures
Jean Baptise Lamarck
The theory of evolution by natural selection is the foundation upon which modern evolution theory is built
Charles Darwin
What is the book written by Charles Darwin and when it is written?
On the Origin of Species, 1859
- Conceived the theory of evolution by natural selection on 1858
- Co-published with Charles Darwin on the origin of species
- Wallace Effect states that natural selection can contribute to reproductive isolation of incipient species by creating barriers and speciations
Alfred-Russel Wallace
First person to recognize that groups of plants and animals could be distinguished from other groups by their ability to mate with one another and produce offspring. He placed such groups of reproductively isolated organisms into a single category, which he called the species.
John Ray
- best known for developing a method of classifying plants and animals. In his famous work, Systema Naturae (Systems of Nature), first published in 1735, he standardized Ray’s use of genus and species terminology and established the system of binomial nomenclature.
- He also added two more categories: class and order. Linnaeus’ four level system became the basis for taxonomy, the system of classification we continue to use today. Another of Linnaeus’ innovations was to include humans in his classification of animals, placing them in the genus Homo and species sapiens.
Carolus Linnaeus
He wrote An Essay on the Principle of Population, which inspired both Charles Darwin and Alfred Wallace in their separate discoveries of natural selection. numbers of humans would eventually lead to famine.
Thomas Malthus
Species may share similar physical features because the feature was present in a common ancestor (homologous structures and analogous).
Anatomy
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.
Examples are forelimbs of whales, humans birds and dogs having similar bone structure despite difference in outside appearance
Homologous Features
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.)
Analogous Feature
DNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are. Like structural homologies, similarities between biological molecules can reflect shared evolutionary ancestry.
These shared features suggest that all living things are descended from a common ancestor, and that this ancestor had DNA as its genetic material, used the genetic code, and expressed its genes by transcription and translation.
Molecular Biology
The global distribution of organisms and the unique features of island species reflect evolution and geological change.
Biogeography
Fossils document the existence of now-extinct past species that are related to present-day species.
Fossils
We can directly observe small-scale evolution in organisms with short life cycles (e.g., pesticide-resistant insects)
Direct Observation
Describes a certain set of organisms grouped based on phenotypic and genotypic similarities
Different taxonomic ranks indicate level of specificity of classification
Using this, Linnaeus proposed a classification system based on taxonomic ranking, transforming taxonomy as a field.
Taxon (pl. Taxa)
8 Major Taxonomic Ranks
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Descriptions of the characteristics of the organism
Comparison, Description
DNA sequences are used to determine whether the organism is indeed novel
Molecular Evidence Analysis
Novel organisms will be given a formal scientific name based on international standards
Naming
The novel species will then be classified into existing ranks or be given a new one based on uniqueness
Classification
Linnaean Naming System
Uses both genus and species name to refer to a unique species
Uses two terms (genus and species), hence ______
Binomial Nomenclature
