Defining Species: Concepts and Speciation

• Defining a species is foundational in biology, involving key concepts.

Morphological Species Concept

• Species are classified based on physical characteristics and structures.
• Useful when genetic data isn't available.
• Can be misleading due to convergent evolution, where unrelated species develop similar features.

Biological Species Concept

• A species is a group of interbreeding organisms that produce fertile offspring.
• Emphasizes reproductive isolation.
• Doesn't apply to asexual organisms or fossils.

Phylogenetic Species Concept

• Species are the smallest group of individuals that share a common ancestor, forming one branch on the tree of life.
• Monophyletic groups consists of an ancestor and all its descendants.
• Synapomorphy are shared derived traits that are unique to a monophyletic group.
• Incorporates genetic data and evolutionary relationships.

Speciation

• New species arise involving two critical steps.

Genetic Isolation

• Populations become separated and gene flow is interrupted.
• Geographic barriers include mountains, rivers, or distances.
• Behavioral changes involves differences in mating rituals or timing.

Genetic Divergence

• Accumulation of genetic differences occurs due to mutation, natural selection, and genetic drift.
• Populations become so different that they can no longer interbreed.

Parsimony in Phylogenetics

• Parsimony Principle states that the simplest explanation with the least assumptions is preferred.
• Application in phylogenetics means the tree with the fewest evolutionary changes is considered most accurate.
• Monophyletic Groups are an ancestor and all its descendants.
• Synapomorphy are shared, derived trait that defines a monophyletic group.

Phylogenetic Trees

• Visual representation of evolutionary relationships.
• Taxa are groups of organisms (species, genera).
• Nodes Points where a lineage splits, representing common ancestors.
• Branches are lines representing evolutionary paths.
• Tips are the ends of branches, representing current species.
• Mapped Traits are characteristics plotted on the tree to trace evolution.
• Homology are similar traits due to shared ancestry.
• Homoplasy are similar traits not due to common ancestry, resulting from convergent evolution.

Radiations and Extinctions

• Adaptive Radiations are rapid evolution of diversely adapted species from a common ancestor.
• Ecological Opportunity new habitats or resources.
• Morphological Innovation is the evolution of new features enabling exploitation of resources.

Types of Adaptive Radiation

• Parallel Adaptive Radiation consists of dispersal, then adaptation (species spread to new areas and then adapt)
• Parallel Adaptive Radiation consists of adaptation, then dispersal (species adapt first and then spread out).
• Mass Extinctions are large-scale events where many species die out in a relatively short period.
• Opens niches for surviving species to diversify.
• Background Extinctions are normal, gradual loss of species over time due to environmental factors.

Land Plant Evolution

• These adaptations allowed plants to thrive on land.
• Cuticle is waxy layer that prevents water loss.
• Cuticle is essential for survival in terrestrial environments.
• Stomata are pores for gas exchange, regulated by guard cells.
• Stomata balances CO2 intake without excessive water loss.
• Vascular Tissue includes Xylem (water transport) and Phloem (nutrient transport).
• Vascular Tissue allows nutrient distribution and structural support.
• Pollen allows fertilization without water.
• Seeds protect the embryo and enable dormancy and dispersal.
• Flowers (Angiosperms) are reproductive structures that attract pollinators.
• Flowers increase genetic diversity and species proliferation.

Hominins

• Human evolution is explored through key traits:

Bipedalism

• Bipedalism is walking on two legs.
• Bipedalism frees hands for tool use and provides energy-efficient locomotion.
• Bipedalism is the main trait that defines hominins as it is what first evolved the hominins from the chimpanzee outgroup.

Height and Sexual Dimorphism

• Height and Sexual Dimorphism includes observations changes in stature and size differences between males and females.
• Height and Sexual Dimorphism has implications for social structures, mating systems, and survival strategies.

Teeth

• Teeth evolved from large canines to smaller, flatter teeth.
• Teeth Provides dietary insights into shift from tough, raw foods to varied diets.

Posture

• Posture has adaptations to spine curvature and pelvic changes for upright walking.

Brain Size

• There has been a significant increase of the brain size over time.
• Brain size correlates to include advanced cognitive functions, tool use, and social interactions.

Chordate Evolution

• Foundational traits defining the chordates:
• Notochord is flexible rod providing skeletal support.
• Notochord has legacy in vertebrates, replaced by the vertebral column.
• Dorsal Nerve Cord is hollow cord dorsal to the notochord.
• Dorsal Nerve Cord development becomes the central nervous system.
• Muscular Tail aids in locomotion.
• Muscular Tail extends beyond the digestive tract.
• Cranium protects the brain.
• Cranium enabled the development of complex sensory organs.
• Vertebral Column is backbone replacing the notochord.
• Vertebral Column enhances structural support and flexibility.
• Amniotic Egg is protective shell with membranes for gas exchange and waste.
• Amniotic Egg enabled reproduction away from water sources.
• Bony Skeleton includes hard tissues like bone and cartilage.
• Bony Skeleton provides support, movement, and protection.
• Convergent Evolution is the development of similar traits in unrelated lineages due to similar environmental pressures, such as wings of bats and insects.
• Ecological Niches includes unique roles in an ecosystem that organisms evolve to fill when a niche opens due to extinction or new habitats.
• Fluctuating climates may have driven hominin adaptations, influencing migration and technological advancements.
• Species richness number of different species present in a specific area or ecosystem.
• Simple count of species and does not consider the abundance of each species or their relative distribution.
• Species diversity considers not only the number of different species (species richness) but also the relative abundance of each species in the area.
• Provides a more comprehensive view of the ecosystem by accounting for both species richness and evenness (how evenly individuals are distributed among the species).
• NPP = energy to growth
• GPP = energy that goes to growth plus energy used in other functions such as repair, cellular resp., reproduction, etc
• Population growth is the increase in the number of individuals in a population over time, which can be exponential or logistic.
• Species richness is the number of species in an ecosystem, while diversity includes both richness and evenness (distribution of individuals among species).
• Rising CO2 levels contribute to global warming, affecting ecosystems, weather patterns, and ocean acidification.
• Positive feedback amplifies changes (e.g., ice melting reduces reflectivity, increasing warming).
• Negative feedback stabilizes systems (e.g., increased CO2 leads to more plant growth, which absorbs CO2).
• Gross Primary Productivity (GPP) is the total energy captured by plants.
• Net Primary Productivity (NPP) is GPP minus energy used in respiration, representing available energy for consumers.
• Bipedalism, larger brains, tool use, language development, and social structures distinguish hominins from other primates.
• Speciation includes isolation (geographic, reproductive), divergence (genetic, behavioral changes), and reinforcement (establishing reproductive barriers).
• Human population growth historically exponential, but trends suggest slowing growth due to lower birth rates and resource limitations.
• Exponential growth is unchecked population increase, while logistic growth levels off at the carrying capacity due to resource limitations.
• Carrying capacity is the maximum population size an environment can sustain based on available resources.
• Chi-Squared Test is a statistical test used to determine if observed data significantly differ from expected values, often applied in genetics and ecology.

Other Key Terms and Concepts

• Genetic isolation.
• Genetic divergence.
• Niche.
• Lots of extinction happened in a short period of time (60%).
• Phylogenetic Trees & Phylogenies.
• Homology.
• Homoplasy.
• Taxa, node, branch, tip, mapped trait.
• Monophyletic groups.
• Synapomorphy.
• Parsimony.

Land Plant Evolution

• Key adaptations: (memorize)
• Cuticles.
• Pores & Stomata.
• Pollen & seeds.
• Vascular tissues.
• Flowers

Chordates evolution

• Key adaptations.
• Notochord.
• Dorsal hollow nerve chord.
• Muscular tail.
• Other traits: Cranium, vertebral column, bipedalism, jaws, bony skeleton, amniotic eggs, limbs, lobed fins.

Hominins: (evolution trends)

• Traits changed over time:
• Height, sexual dimorphism, teeth, posture, braincase/size.
• Transitional forms: lobed fins.
• A trait that was a mix of ancestors trait and descendants trait (transition of evolution).
• Population Growth.
• Lamda: n1/n0.
• Nt = N0 * (lamda)^t.