Lab 3 - Evolution and Classifying Diversity Flashcards
How does evolution generally drive diversity?
Divergent Speciation:
* Biological and Morphological Species Concepts
* Anagensis - Phyletic Transformation
* Cladogensis - Divergent Speciation
Biological Species Concept
Biological and Morphological Species Concepts
Divergent Speciation
- A species as a group of organisms that can interbreed and produce fertile offspring
- However, paleontologists who study fossils cannot use this concept.
What do paleontologists rely on instead?
+ what advantages?
- Instead, they rely on the Morphological Species Concept: classifies species based on their physical characteristics.
- Offers an advantage: the ability to observe how organisms change over time
There are two main theories about how evolution occurs:
- Anagenesis (gradual change within a species)
- Cladogenesis (divergent speciation - the splitting of a species into two or more new species).
Anagensis - Phyletic Transformation
- Anagenesis: where a single species gradually changes over time without branching into separate species.
- As the ancestral species evolves and adapts to its environment, it eventually becomes a new species - WITHOUT increasing the overall diversity of life
Cladogensis
- Cladogenesis occurs when a single species splits, forming new species
- (It’s like a family tree branching out, with new species emerging from a common ancestor)
- Increases biodiversity
Isolation-causing cladogenesis can occur in two ways:
- Allopatric speciation
- Sympatric speciation
Allopatric speciation
Isolation-causing cladogenesis can occur in two ways:
involves physically separating populations by a geographic barrier, such as a river or mountain range
Sympatric speciation
Isolation-causing cladogenesis can occur in two ways:
occurs within a single population without geographic isolation
What does Allopatric speciation result in?
Isolation-causing cladogenesis can occur in two ways:
- This causes reproductive isolation and the potential formation of new species due to genetic drift and natural selection acting independently on the separated populations.
Sympatric speciation
Isolation-causing cladogenesis can occur in two ways:
Sympatric speciation can be driven by genetic preferences for certain courtship behaviours or ecological niches, leading to reproductive isolation and, ultimately, the divergence of the population.
In allopatric and sympatric speciation, what drives the emergence of a new species?
evolution via natural selection
Phyletic gradualism
Pace and Pattern of Evolutionary Change
the theory that species evolve slowly and gradually over time, gradually accumulating changes until they become distinct enough to be considered a new species.
Phyletic gradualism - do most species follow this slow evolution?
+ WHY?
- Change appears to occur rapidly.
- This could be explained by unconformities, removing sections of the geological record and making a record of gradual change appear to “jump” suddenly
Punctuated Equilibrium
Pace and Pattern of Evolutionary Change
- Unlike the slow and gradual processes inferred by gradualism, Punctuated Equilibrium proposes that evolution can be characterized by rapid change that may proceed or be followed by long periods of stability or “stasis” with little change
- Sudden changes could be driven by natural events such as rapid climate change that may favour or present opportunities for certain members of a population over others.
Random Walks
Pace and Pattern of Evolutionary Change
- Random walks: trends in fossil species that aren’t caused by natural selection. Imagine flipping a coin many times; you’ll often see runs of heads or tails.
- Similarly, species can change in seemingly random ways, but these changes aren’t completely random:
- There are often limits, or “bounding surfaces,” that prevent certain traits from going too far in one direction.
Which pattern of evolution is supported by the fossil record?
- Studies done align with the theory of punctuated equilibrium, which suggests that evolution often occurs in bursts of rapid change followed by long periods of stability.
- Doesn’t mean that gradualism doesn’t happen.
- Gradualism might be more common in populations with high reproduction rates, such as microorganisms
Life is arranged in a hierarchical system, subdivided into the three domains and then subdivided until we reach individual species.
WHAT ARE THESE? (9)
Classifying the Modern Biosphere
- Life
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Cladistics
a way of classifying living things based on their shared characteristics.
In cladistics, a clade..
- Is a group of organisms that share a common ancestor and all its descendants
- The more traits two organisms share, the more closely related they are.
Cladogram
diagram used in cladistics that visually displays relationships between organisms.
What is considered a chordate?
Types of phylum
- A phylum that contains all animals with a nerve cord called a notochord that runs down the back of the animal.
- Humans occupy a subphylum of Phylum Chordata called the Vertebrates (Vertebrata) that encase the notochord in bone or cartilage.
- NOTE: phylum is a broader classification that a clade
Outgroup
- organism to which all the other organisms in the cladogram (sometimes called the “ingroup”) are most distantly related
- kind of building on clade
Tetrapod clade
Types of clades
all vertebrates that have or had four limbs
