Untitled Quiz

Biological Species Concept

• A species is a group of populations whose members have the potential to interbreed and produce viable offspring.
• Viable offspring are healthy juveniles that mature into fertile adults.
• This definition only applies to sexually reproducing organisms, not asexual ones like bacteria or amoeba.

Reproductive Isolation

• Reproductive barriers separate species.
• A reproductive barrier is anything that prevents two individuals from producing viable offspring.
• Prezygotic and postzygotic barriers

Prezygotic Barriers

• Spatial Isolation: species living in the same area may never encounter each other (e.g., occupying different habitats).
• Behavioral Isolation: breeding does not occur due to incorrect mating behavior (e.g., courtship rituals).
• Temporal Isolation: members of closely related species breed at different times (e.g., different times of the day or year).
• Mechanical Isolation: similar species cannot breed because they are anatomically different (e.g., plants and pollinators, insects' sex organs).
• Gametic Isolation: gametes meet, but fail to fuse and produce a zygote.

Postzygotic Barriers

• Reduced Hybrid Viability: fertilization occurs and produces a zygote, but the offspring do not survive or are significantly less healthy.
• Reduced Hybrid Fertility: hybrids are viable, but sterile (e.g., mules).
• Hybrid Breakdown: first-generation hybrids are fertile, but subsequent generations are infertile or unhealthy (e.g., cotton).

Speciation

• Speciation is the process by which one species diverges into two species.
• Two requirements
  • Geographic isolation of populations
  • Genetic divergence (mutations occur causing reproductive barriers).
• Allopatric speciation: members of the same species become separated due to a geographic barrier and evolve into two species.
• Allopatric speciation is an example of speciation occurring when populations are geographically separated.
• Humans and chimpanzees are closely related.
• Humans and lemurs are distantly related.

Convergent Evolution

• The independent evolution of similar structures in unrelated species.
• Similar adaptations to similar environments.
  • Example: desert plants.
  • Example: having spines/thorns (modified leaves/branches to prevent predation and help in water conservation).
  • Example: having fleshy stems to store water.

Divergent Evolution

• Groups from the same common ancestor evolve and accumulate differences, resulting in new species that can be quite different.

Rates of Evolution

• Gradualism: slow speciation of organisms brought about by the slow accumulation of favorable characteristics over time (e.g., beak size of finches, horse evolution).
• Punctuated equilibrium: quick, fast burst of new species followed by longer periods with little evolution (e.g., bacteria, insects).

Classification

• Every organism is assigned to one of three domains: Bacteria, Archaea, and Eukarya.
• Organisms are further classified into successively more precise categories (kingdom, phylum, class, order, family, genus, species).
  • Naming system: Dear King Phillip Came Over For Great Soup.
• Binomial nomenclature: using two names to classify every organism (genus and species).
  • Example: Homo sapiens, Escherichia coli
• Rules of Binomial nomenclature: 1st letter of the genus is capitalized, species name is not capitalized, both are italicized when typed, both underlined when handwritten.

Eukaryotic cells evolve from prokaryotic cells

• Endomembrane system developed from infoldings of the plasma membrane (nucleus, ER, Golgi).
• Endosymbiosis: one species living inside another host species (mitochondria and chloroplasts started out as separate cells, have their own DNA, resemble prokaryotic DNA).