Biology Exam 2 Review

Major Eras of Earth's History

• Precambrian

  • Dominated the majority of Earth's history.

  • Included mostly prokaryotic life and the first simple animals.

• Paleozoic

  • Introduction of the first plants and vertebrates (fish, amphibians, reptiles).

• Mesozoic

  • Introduction of the first birds and mammals, and significant diversification of reptiles, including dinosaurs.

• Cenozoic

  • Major diversification of mammals, birds, and flowering plants.

Key Evolutionary Concepts

• Macroevolution

  • Describes evolutionary changes occurring above the species level.

• Gradualism

  • Mutations gradually lead to differences in offspring over time, but faces issues in describing sudden changes in fossil records.

• Punctuated Equilibrium

  • Suggests that evolution might occur in bursts with periods of little change, though lacks a genetic mechanism explanation.

• Adaptive Radiation

  • Rapid diversification often following mass extinctions or new adaptations, lacking genetic mechanistic explanations.

• Allopatric Speciation

  • Occurs when geographic barriers prevent mating between populations.

• Sympatric Speciation

  • Happens when species are separated due to microhabitat features or polyploidy.

• Inbreeding

  • Refers to mating between closely related individuals.

Theories on Origin of Organic Chemicals

• Hydrothermal Vent Hypothesis

  • Life could have originated through concentrated chemical reactions at superheated ocean vents; however, the complexity arising from chaos is questioned.

• Warm Pond Hypothesis

  • Suggests that organic molecules formed in small ponds through wet-dry cycles, but these conditions struggle against competing reactions and UV destructive effects.

• Meteorite Hypothesis

  • Proposes biomacromolecules originated from meteorites, though questions linger on the continuity of complexity building.

The First Genetic Material

• RNA is considered the first genetic material due to its dual role as both an enzyme and genetic material, resolving the DNA-protein origins dilemma.

• Stability issues with RNA surface, as it degrades easily over time.

Stages of Developing the First Life

1. Simple organic molecules formation.

2. Transition to complex organic molecules.

3. Life-like chemical reactions becoming packaged.

4. Development of self-replicating chemical reactions.

Oxygen in Earth's Atmosphere

• Oxygen production is largely attributed to early life forms.

Endosymbiont Theory

• Proposes that eukaryotic organelles like chloroplasts and mitochondria originated from engulfed prokaryotes, as they contain their own DNA and replicate analogously to prokaryotic cells.

Major Hominids

• Ardipithecus

  • Early bipedal ancestor, possibly still arboreal.

• Australopithecus

  • Larger brain capacity, fully upright, utilized tools.

• Homo habilis

  • Used specialized tools for meat processing.

• Homo erectus

  • Larger brain, potential controlled use of fire.

• Homo neanderthalensis

  • Largest brain among hominids, displayed technology and perhaps burial practices.

• Homo sapiens

  • Modern humans, advanced communication, and problem-solving capabilities; interbred with Neanderthals.

Out of Africa Hypothesis and mtDNA

• Evidence points to a singular origin of modern humans in Africa, supported by genetic research tracing back to a single woman approximately 200,000 years ago.

Biomes Overview

• Desert

  • Characters include dry climate, seasonal temperatures, and limited animal life.

• Tropical Rainforests

  • High diversity due to consistently wet and warm conditions.

• Savannah

  • Characterized by grasslands with seasonal rainfall and large herbivores.

• Prairies

  • Similar to savannahs but contain fewer trees.

• Taiga

  • Predominantly coniferous forests, animals often migrate or hibernate.

• Tundra

  • Cold ecosystem with permafrost and few trees.

• Deciduous Forests

  • Characterized by broad-leaved trees, seasonal rainfall, and temperature variations.

• Transitional Zones

  • Marshes - Grass-dominated wetlands with high diversity.

  • Swamps - Tree-dominated wetlands with high diversity.

Thermocline and Turnover

• Thermocline

  • Temperature transition zone within water bodies.

• Turnover

  • Vertical cycling of water in lakes; affected by seasonal temperature fluctuations, with impacts from global warming.

Biomass Distribution

• Most biomass exists within producers (photosynthetic organisms).