Honors Biology Unit 9



  • Adaptive radiation- Process by which one species evolves and gives rise to many descendants species that occupy different ecological niches ex. Radiation of mammals after mass extinction that killed dinosaurs 65 m years ago


  • Allopatric speciation - process of speciation that occurs with geographic isolation, most common form of speciation via evolution


  • Know different barriers (behavioral, geographic/habitat, temporal, mechanical, gametic)

    • Behavioral: isolation caused by differences in courtship or mating behaviors, changes in courtship dances, chemical signals, courtship songs, etc. used to attract mtes

    • Geographic/habitat: Isolation caused by physical barriers that divide a population into 2 or more groups; aka separation of populations as results of geologic change

      • Barriers includes rivers, mountains, dried lakebeds 

      • How long they remain separated depends on species ability to get around 

      • Once separated, a splinter population may follow its own evolutionary course (genetic drift) 

      • Speciation has only occurred if one population can no longer breed with other population 

    • Temporal barriers: Isolation that exists when timing prevents reproduction between populations 

      • Here timing is key: 2 similar species may breed in different seasons or have separate pollination periods, a way to avoid competition 

    • Mechanical barriers: Isolation that exists when physical incompatibility prevents reproduction between populations 

      • Here reproductive parts are altered so not interchangeable (due to size, shape, and location) 

      • Thought of as not being a major driver of speciation for animals, but extent to how often this results in speciation is unknown

    • Gametic barriers: Isolation that exists when molecular incompatibility of eggs and sperm prevents reproduction between populations 

      • Here chemical signlas released by eggs and sperm may cause them to not be attracted to each other or eggs and sperms are prevented from fusing with each other, when fusion does occur, but zygote dies without further developmemt 

  • Cladogram (derived characteristics) 

    • A phylogenetic tree that specifies derived characteristics of clades 

      • Branches: each branch represents a lineage. The point where branches split is called a node, which represents a common ancestor 

      • Derived characteristics: these are traits that are present in an organism but were absent in the last common ancestor of the group. They help to define the branches. 

      • Outgroup: This is a species or group that is closely related but not part of the group being studied. 

  • Coevolution

    • Process in which two or more species evolve in response to changes in each other 

    • Can be beneficial for one or both species in relationship 

  • Convergent evolution (analogous structures) 

    • A process where different species develop similar traits or structures independently, often because they live in similar environments or face similar challenges. These similar traits are called analogous structures. 

    • For example, the wings of birds and bats are analogous structures. Both are used for flying, but birds and bats evolved their wings separately. Birds are more closely related to dinosaurs, while bats are mammals. Despite their different evolutionary paths, the need to fly led to the development of wings in both groups 

  • Divergent evolution (homologous structures)

    •  A process where two or more related species become more different over time, often due to different environmental pressures or niches. This can lead to the development of homologous structures, which are body parts that have a similar structure but may serve different functions in different species. 

    • For example, conside the forelimbs of mammals like humans, bats, and whales. They all have a similar bone structure, indicating a common ancestor, but they have evolved to perform different functions; grasping in humans, flying in bats, and swimming in whales. This is a classic example of homologous structures resulting from divergent evolution

  • Evolution 

    • Process that explains how species change over time. It’s based on the idea that all living organisms share a common ancestor and have gradually changed through natural selection, mutations, and genetic drift 

  • Extinction

    • When a species, or a group of organisms, completely disappears from the planet. This can happen for various reasons, such as changes in the environment, loss of habitat, overhunting, or natural disaster

  • Fossil (geological) record 

    • The fossil record is like a historical archive of life on earth, it consists of the remains or imprints of organisms preserved in rock layers over millions of years. 

    • Fossils: These are the preserved remains or traces of ancient organisms. They can be bones, shells, footprints, or even lead impressions 

    • Formation: fossils typically form when an organism is buried quickly after death, often in sediment like mud or sand. Over time, these sediments harden into rock, preserving the shape of the organism 

    • Geological layers: different layers of rock, called strata, represent different periods in earth’s history. By studying these layers, scientists can learn about the organisms that lived at various times 

    • Evolutionary evidence: the fossil record provides evidence of how life has evolved over time, showing changes in species and the emergence of new ones 

  • Genetic drift -change in allele frequencies due to chance (random, unpredictable event) alone 

  • Typically occurring in populations that are small, and more likely to be affected by chance 

  • Causes a loss of genetic diversity in a population 


  • Genomics/DNA  - 

  • Geographic isolation

    • Physical separation of a group of individuals from others of the same species 

  • Gradual adaptation 

    • Small changes can accumulate over long periods of time 

    • Originally written by Darwin 

    • Idea that new species arose through gradual transformations of ancestral species

  • Hybridization

    • The crossing of two different species that share common genes

    • May happen between many groups of birds and mammals when similar species ive in close proximity to each other and individuals can’t find mates within their own species 

  • Macroevolution -  major evolutionary transition from one type of organism to another - can include 3 things : origin of new species - extinction of species - evolution of major new features of living things( wings , fins , flowers , and fruit)

  • Mass extinction (know how this compares to background extinction) 

  • Microevolution - change in allele frequency within a population; aka change in a populations gene pool - all still same species - animals - breeds&plants- varieties

  • Migration/gene flow 

  • Mutations -Random changes in DNA of a gene ,Change can form a new allele Mutations in reproductive cells can be passed on to offspring

  • Natural /artificial selection 

  • Phenotype - Expression of a trait Phenotypes are produce by one or more genes 

  • Phylogenetic tree - Diagram shows how species are related through evolution by common ancestor ( length of arms/branches conveys length of time)

  • Phylogeny 

  • Population - Individuals that belong to the same species that are in the same place at the same time 

  • Punctuated equilibrium 

    • Theory that states that there are rapid and sudden bursts of evolutionary activity (speciation) followed by long periods of stability (little evolutionary change) 

    • Theory proposed by Eldrege and Gould in 1972

    • Based off of evidence from repeating patterns found in fossil record

  • Reproductive isolation

    • Final stage in speciation, in which members of isolated populations are either no longer able to mate or no longer able to produce viable offspring 

    • Members are either: 

      • Not physically able to mate with each other 

      • Not able to produce offspring that survive and reproduce 

      • These are the final steps to becoming separate species and over time this can lead to speciation

  • Speciation (know the two things that drive this)

    • Evolution of 2 or more species from one existing species; aka the rise of two or more species from one existing species

    • Geographic and reproductive isolation drive this

  • Species 

    • A population or group of populations whose members have the ability to breed in nature and produce fertile offspring

  • Sympatric species 

    • The evolution of one species into two groups without geographic isolation 

    • Occurs due to polypoidy 

  • Taxonomy (know D-Sp in order; know the 6 kingdoms & 3 Domains; Linnaeus; know how properly name specie name)

    • Taxonomy order (from broad to specific) 

      • Domain 

      • Kingdom 

      • Phylum 

      • Class

      • Order

      • Family 

      • Genus

      • Species 

    • 3 Domains: 

      • Bacteria- single celed organisms without a nucleus 

      • Archaea- similar to bacteria but with different genetic and biochemical characteristics 

      • Eukarya- organisms with cells that contain a nucleus 

    • 6 kingdoms

      • Animalia- multicellular, eukaryotic organisms that are usually mobile 

      • Plantae - multicellular, eukaryotic organisms that typically perform photosynthesis 

      • Fungi- eukaryotic organisms that absorb nutrients from organic materials 

      • Protista- mostly single-celled eukaryotes that don’t fit into the other kingdoms 

      • Eubacteria- true bacteria, found everywhere 

      • Archaebacteria - ancient bacteria, often found in extreme environments 

    • Linnaeus: Carl Linnaeus is known as the “father of taxonomy”. He developed a system for naming and classifying organisms 

    • Proper naming of species: 

      • The scientific name of a species is called a binomial nomenclature 

      • It consists of two parts: the Genus name (capitalized) and the species name (lowercase) 

      • Both parts are italicized or underlined.
        For example, Homo sapiens. 

  • Temporal isolation - 

    • A type of reproductive isolation that occurs when two or more species reproduce at different times