EXAM II - Biodiversity and Evolution of Plants

Great Oxidation Event

An event that occurred 2.4 billion years ago, resulting in a buildup of oxygen in the atmosphere.

Why is Great Oxidation Event important?

It was toxic to many anaerobic organisms but promoted more aerobic organisms to evolve into more complex form due to more efficiency in energy.

Cyanobacteria

Single-celled bacteria that use photosynthesis. Over hundreds of millions of years, they transformed the Earth from having little oxygen to supporting various oxygen dependent life.

Cyanobacteria and plants

Chloroplasts, the part that perform photosynthesis in plants, evolved from ancient cyanobacteria. A larger cell engulfed a cyanobacterium, a process called endosymbiosis.

Earth Systems

• Climate

• Hydrosphere

• Geosphere

• Atmosphere

Example of Feedback System and Biodiversity

Through a negative feedback loop:

• Deer increase → Wolves have more food → Wolf population grows

• More wolves → Hunt more deer → Deer population drops

Stops one species from dominating the other and maintains biodiversity.

Three Main Eras of Earth’s History

Paleozoic, Mesozoic, and Cenozoic.

Evolutionary Innovations in Paleozoic

• Amniotic egg

• Vascular Systems

• Biomineralization

Importance of the Amniotic Egg

It protected the embryo in a waterproof capsule and allowed vertebrates to reproduce on land, moving away from the reliance on aquatic environments.

Importance of Vascularization

Vascular tissues allows for plant to move nutrients and waters from underground and upwards, allowing plants to grow taller. It transformed the Earth’s atmosphere by sequestering carbon and releasing mass amounts of oxygen.

Importance of Biomineralization

Allowed organisms to develop hard structures, such as shells and skeletons, providing protection from predators and structural support. It contributed to the diversification of animal life during the Cambrian Explosion.

Evolutionary Innovations in Meisozoic

• Flight

• Angiosperms (Flowering Plants)

• Mammals

Importance of Flight

Species developed powered flight, allowing them to exploit new habitats.

Importance of angiosperms

Evolved flowers and fruits, allowing more efficient pollination and seed dispersal. This promoted diversity and coevolution, as seeds can be dispersed farther and coevolution can happen between plants and pollinators.

Importance of mammal evolution

Mammals evolved specialized adaptations, including fur, milk production, and endothermy (warm-bloodedness), which improved survival, temperature regulation, and offspring development.

Permian extinction

Also known as the Great Dying. It occurred approximately 252 million years ago, marking the end of the Paleozoic Era. It was the largest mass extinction in Earth's history, with ~90%+ of all species lost.

What caused the Permian extinction?

Massive volcanic eruptions in Siberia (Siberian Traps) released large amounts of greenhouse gases, causing global warming, ocean acidification, and ocean oxygen depletion (anoxia). These environmental changes disrupted ecosystems and led to widespread extinction.

K-Pg Extinction

Occurred approximately 66 million years ago, marking the end of the Mesozoic Era.

What caused the K-Pg extinction?

A massive asteroid struck Earth in present-day Mexico, releasing dust and gases that blocked sunlight, causing global cooling, reduced photosynthesis, and food chain collapse, leading to widespread extinction.

What are the evidences of the asteroid impact?

• High concentrations of iridium, an element rare in Earth's crust but common in asteroids.

• Shocked quartz: Minerals deformed by the extreme pressure of an impact.

• Chicxulub crater: A massive impact crater in Mexico dating to approximately 66 million years ago.

Photosynthesis Equation

6CO2 + 6H20 = C6H12O6 + 6O2

Reactants that Cyanobacteria Use

Water and Carbon Dioxide

Ediacaran Period

Occurring 635–539 million years ago, marked the emergence of some of the earliest large, complex multicellular organisms, including early animals.

Why was the Ediacaran period important?

It marked a major step in the evolution of complex life, including early animals, and laid the foundation for the rapid diversification of animals during the Cambrian Explosion.

What were three significant evolutionary developments during the Ediacaran Period?

• Bilateral symmetry

• Cephalization

• Gut tracts (digestive tracts)

Importance of bilateral symmetry

Allowed more efficient directional movement and the development of specialized body regions. It allowed animal to move back and forth, in a direction.

Importance of cephalization

As a result of bilateral symmetry, concentrated sensory organs and nervous tissue at the head, improving environmental awareness and responses to stimuli.

Importance of digestive tracts

Allowed one-way food processing (mouth to anus), improving digestion and nutrient absorption.

What was the Cambrian Explosion?

A period of rapid diversification of marine animal life approximately 539 million years ago.

What was the evolutionary significance of the Cambrian Explosion?

The emergence and diversification of many major animal body plans, increasing the complexity and diversity of marine ecosystems.

What major event occurred during the Silurian/Devonian Periods?

Plants increasingly colonized land, evolving adaptations that allowed them to survive and reproduce in terrestrial environments. This change the

What was the evolutionary significance of plants moving onto land?

Plants developed vascular tissues, roots, and leaves, establishing terrestrial ecosystems and providing habitats and food sources for other organisms.

What major event occurred during the Devonian/Carboniferous Periods?

The rapid diversification of life on land. During the Devonian, some fish evolved limbs and began transitioning onto land, while the Carboniferous saw the spread of vast forests, amphibians, and early reptiles.

What was the evolutionary significance of the explosion of life on land?

The diversification of terrestrial organisms established complex land ecosystems and food webs. The evolution of limbs and lungs allowed vertebrates to move onto land, while the amniotic egg enabled reptiles to reproduce away from water.

What major event occurred during the Triassic/Jurassic Periods?

The rise of dinosaurs, which first appeared during the Triassic and became dominant terrestrial vertebrates during the Jurassic.

What was the evolutionary significance of the rise of dinosaurs?

Dinosaurs diversified into numerous ecological niches. Herbivores shaped vegetation through grazing, and carnivores regulated prey populations, influencing food webs and becoming dominant land animals.

What major event characterized the Cenozoic Era?

The rise of mammals followed the K-Pg extinction, characterized by their rapid diversification and expansion across terrestrial ecosystems.

What was the evolutionary significance of the rise of mammals?

Mammals rapidly diversified into herbivores, carnivores, and omnivores, developing specialized teeth, limbs, and body structures. They occupied ecological niches left vacant by dinosaurs, becoming dominant in many terrestrial ecosystems.

What is the Anthropocene?

A proposed geological epoch characterized by humans becoming a major force shaping Earth's landscapes, ecosystems, and climate.

What is the evolutionary significance of the Anthropocene?

Human activities drive habitat loss, species extinctions, and environmental changes, creating new selective pressures that influence evolution and biodiversity.

Bryophytes (Mosses)

Nonvascular plants lack true roots, stems, and leaves. They reproduce through spores and require water for fertilization. They represent early adaptations to life on land, with protective structures that reduce water loss and protect embryos. Their lack of vascular tissue limits their size and growth.

Ferns

Seedless vascular plants have true roots, stems, and leaves. They reproduce through spores and still require water for fertilization. They are significant because they have evolved vascular tissue.

Gymnosperms

Vascular plants that produce naked seeds, usually in cones, rather than flowers or fruits. They reproduce through pollen and seeds without requiring external water for fertilization. The evolution of pollen and seeds allowed reproduction without free-standing water.

Angiosperms

Vascular plants that produce flowers and seeds enclosed within fruits. They use flowers for reproduction and fruits for seed protection and dispersal. The evolution of flowers and fruits improved pollination efficiency, seed protection, and dispersal.

How did plants affect Earth's climate, and how did climate affect plant evolution?

Plants reduced atmospheric CO₂ through photosynthesis, contributing to global cooling and influencing rainfall through transpiration. In turn, changes in temperature and rainfall shaped plant evolution and distribution, favoring adaptations such as seeds, vascular tissues, and waxy cuticles for survival in drier environments.

How did the development of tree roots impact Earth's systems?

Tree roots broke down rocks, increasing weathering. This process used CO₂ from the atmosphere, eventually storing carbon in ocean sediments. As atmospheric CO₂ decreased, the greenhouse effect weakened, causing global cooling.

What were the first animals to venture onto land?

Arthropods, particularly early millipedes and arachnids, were among the first animals to colonize land, developing adaptations such as exoskeletons to prevent water loss and jointed legs for movement.

Why is Tiktaalik roseae important?

It had both fish-like features (scales and fins) and land-animal features (a neck, ribs, and limb-like bones), providing evidence of how vertebrates evolved adaptations for moving onto land. It was a transitional fossil.

What are the key characteristics and evolutionary significance of arthropods?

They have segmented bodies, jointed appendages, and hard exoskeletons. Their exoskeletons provided protection and reduced water loss. Jointed legs enabled efficient movement, allowing them to become some of the earliest animals to colonize land.

What are the key characteristics and evolutionary significance of amphibians?

They evolved from fish-like ancestors and developed limbs and lungs, allowing vertebrates to move onto land. Most still depend on water for reproduction because their eggs lack protective shells.

What are the key characteristics and evolutionary significance of reptiles?

They evolved waterproof, scaly skin and amniotic eggs, which protected embryos from drying out. These adaptations reduced dependence on water for reproduction, allowing reptiles to colonize drier terrestrial environments.

What are the key characteristics and evolutionary significance of mammals?

Mammals evolved fur, milk production, and endothermy . These adaptations improved temperature control, offspring survival, and the ability to occupy diverse environments, contributing to their diversification.

What are sauropsids?

Amniotes that include reptiles, dinosaurs, and birds. Their adaptations to land allowed them to diversify and dominate many terrestrial ecosystems.

How long did dinosaurs dominate the world and how?

For about 170 million years. Key adaptations included air sacs that move air through the respiratory system, air filled space inside their bones that made it lighter, and through laying eggs make able to grow more large.

Theory Behind Dinosaur Diversification

Adaptive radiation is a theory explaining how dinosaurs diversified from a common ancestor into many species adapted to different ecological niches. Fossil research supports this diversification, showing how dinosaurs evolved different diets, body sizes, and adaptations.

Mass extinction

A widespread and rapid drop in global biodiversity where about 75% or more of the Earth's species die out within a relatively short period of geological time. Dramatic extinction and dramatic climate change occurs.

Ecology

Explains the interaction between organisms and their environment. Both biotic and abiotic factors.

Evolution

Explains how species originated.

Quaternary Period

The current and most recent geological period of the Cenozoic Era, spanning from 2.6 million years ago to the present day.

Megafauna

Refers to large or giant animals—most commonly land mammals—that weigh over 45 kg (100 lbs)

What did humans have first large brains or up-right posture?

Upright posture (bipedalism) came long before large brains, about 6-7 million years, whilst large brains started appearing 2-3 million years ago.

How does climate impact biodiversity and evolution?

Climate influences which species can survive and reproduce. Changes in temperature, rainfall, and habitats create selective pressures that drive adaptations, migration, and speciation. Extreme climate changes can also cause extinctions, reducing biodiversity.

Who were Neanderthals?

An extinct group of ancient humans.

When and where did Neanderthals live?

They lived approximately 400,000 to 40,000 years ago in Europe and southwestern to central Asia. They were closely related to modern humans and adapted to cold climates.

Community ecology

An assemblage of species living close together for potential interaction is called a community. Species often have interactions such as competition, predation, parasitism, and mutualism.

Competitive Exclusion Principle

Theory that the species that is better at gaining the limited resource will eventually eliminate inferior competition.

Coexistence Principle

Niche differences hinder competitive exclusion, which helps maintain diversity. Resources partitioning.

Plants Terrestrial Adaptions

• Roots

• Vascular Tissues

• Prevention of water loss

• Stomata

• Reproduction