Biology 1B Study Guide

What is evolution?

A change in allele frequencies within a population over successive generations.

What are the forces that can cause evolutionary change within a population?

Natural selection, mutation, gene flow, genetic drift, non-random mating.

What is a bottleneck event?

A drastic reduction in population size due to a disaster, causing a loss of genetic diversity.

What is the founder effect?

A small group of individuals establishes a new population, carrying a subset of the genetic diversity from the original population.

What does the Hardy-Weinberg Principle of Equilibrium state?

Allele frequencies in a population remain constant in the absence of evolutionary influences.

What are the conditions for Hardy-Weinberg equilibrium?

No mutation, random mating, no natural selection, large population size, no gene flow.

What is convergent evolution?

Unrelated species evolve similar traits due to similar environmental pressures.

What is divergent evolution?

Related species evolve different traits due to different environmental pressures.

What are homologous structures?

Structures that are similar in related organisms due to shared ancestry.

What are analogous structures?

Structures that are similar in function but not due to shared ancestry.

What is allopatric speciation?

Species formation due to geographic isolation.

What is peripatric speciation?

A small group is isolated at the edge of a larger population.

What is parapatric speciation?

Speciation occurs in adjacent populations with a gradient of environmental factors.

What is sympatric speciation?

Speciation that occurs without geographic isolation, often due to ecological or behavioral factors.

What are prezygotic barriers?

Barriers that prevent mating or fertilization from occurring.

What are postzygotic barriers?

Barriers that occur after fertilization, preventing proper development or reproduction.

What is directional selection?

Natural selection that favors one extreme phenotype.

What is stabilizing selection?

Natural selection that favors average phenotypes.

What is diversifying (disruptive) selection?

Natural selection that favors extreme phenotypes at both ends.

What is reinforcement in a hybrid zone?

Strengthening of reproductive barriers between two species.

What is fusion in a hybrid zone?

Two species merge into one as reproductive barriers weaken.

What is stability in a hybrid zone?

Continued hybridization with no significant speciation.

What is a cline?

A gradual change in a trait or genetic variation across a geographic area.

What is evolutionary fitness?

The ability of an individual to survive, reproduce, and pass on its genes relative to others.

What is sexual selection?

Natural selection driven by mate choice.

What is intrasexual selection?

Competition between members of the same sex for mates.

What is intersexual selection?

Mate choice by the opposite sex.

What distinguishes viruses from viroids?

Viruses are infectious particles made of nucleic acids and protein, while viroids are small circular RNA molecules that infect plants.

What distinguishes viruses from prions?

Viruses are non-living infectious particles, while prions are infectious proteins causing diseases by misfolding other proteins.

What are prokaryotic organisms?

Simple cells without a nucleus, such as bacteria.

What are eukaryotic organisms?

Complex cells with a nucleus and organelles, such as animals, plants, and fungi.

How do prokaryotes reproduce?

Asexually through binary fission.

What is horizontal gene transfer?

The process by which bacteria exchange genetic material through conjugation, transformation, and transduction.

What roles do bacteria play in ecosystems?

Bacteria serve as decomposers, nitrogen fixers, and symbionts.

What is the endosymbiotic theory?

The theory that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by an ancestral eukaryote.

What evidence supports the endosymbiotic theory?

Presence of double membranes, circular DNA, and similarities to certain prokaryotes.

What is the evolutionary relationship of protists with other major groups?

Protists are a paraphyletic group, sharing a common ancestor with plants, fungi, and animals.

How are fungi evolutionarily related to animals?

Fungi are more closely related to animals than to plants.

What characteristics do fungi share with plants?

Both are multicellular (except yeasts).

What characteristics do fungi share with animals?

Both are heterotrophic and digest food external to their cells.

How do fungi differ from bacteria?

Fungi have cell walls made of chitin, while bacteria have cell walls made of peptidoglycan.

What is the metabolism of fungi?

Fungi are heterotrophic and use absorptive nutrition.

What role do fungi play in ecosystems?

Fungi serve as decomposers, facilitating nutrient cycling, and forming mutualistic relationships.

What challenges do plants face on land?

Desiccation, gravity, reproduction, nutrient uptake.

What adaptations have allowed plants to colonize land?

Cuticle, vascular tissue, stomata, roots, and seeds.

What are nonvascular plants?

Plants that lack vascular tissue and depend on water for reproduction, such as mosses.

What are seedless vascular plants?

Plants that have vascular tissue but reproduce via spores, such as ferns.

What are seed plants?

Plants with vascular tissue and seeds, including gymnosperms and angiosperms.

What are progymnosperms?

Early seedless vascular plants.

What are gymnosperms?

Seed plants that do not have flowers.

What are angiosperms?

Flowering plants with seeds encased in fruit.

What defines monocots?

One cotyledon, parallel leaf veins, and scattered vascular bundles.

What defines dicots?

Two cotyledons, branched leaf veins, and vascular bundles in a ring.

What is water potential?

The tendency of water to move from areas of high potential to low potential.

What is transpiration?

Evaporation of water from leaves, creating negative pressure that draws water upward.

What regulates the opening and closing of stomata?

Guard cells.

What are the key features of kingdom Animalia?

Multicellular, heterotrophic, eukaryotic, lack cell walls, motile in life cycle, presence of nervous and muscular systems.

What role do Hox genes play in animal development?

Hox genes regulate the development of body plans and segment identity during embryogenesis.

What distinguishes Parazoa from Eumetazoa?

Parazoa are the simplest animals lacking true tissues, while Eumetazoa have true tissues organized into organs.

What are the major characteristics of Cnidaria?

Radial symmetry, diploblastic tissue level, incomplete digestive system, and simple nerve net.

What defines Lophotrochozoa?

Bilateral symmetry, triploblastic, includes animals with a lophophore or trochophore larvae.

What defines Ecdysozoa?

Animals that grow by molting their exoskeleton.

What defines Deuterostomia?

Animals whose embryonic development includes radial cleavage and formation of the anus first.

How evolved jaws in animals?

Jaws evolved from gill arches in early fish for feeding.

What is the evolutionary path of vertebrates?

Fish → Amphibians → Reptiles → Mammals/Birds.

What are the derived characteristics of fish?

Vertebral column, gills, scales.

What are the derived characteristics of amphibians?

Moist skin, limbs, life cycle with aquatic and terrestrial stages.

What are the derived characteristics of reptiles?

Amniotic eggs, scales, ectothermic.

What are the derived characteristics of birds?

Feathers, endothermic, beaks, hard-shelled eggs.

What are the derived characteristics of mammals?

Hair, mammary glands, endothermic, live birth in most.

What distinguishes monotremes?

Egg-laying mammals.

What distinguishes marsupials?

Pouched mammals.

What distinguishes eutherians?

Placental mammals that develop inside the womb.

How is bioenergetics related to body size?

Larger animals generally need more energy to maintain metabolic processes.

How do positive and negative feedback mechanisms function in homeostasis?

Negative feedback counters a stimulus, while positive feedback amplifies a stimulus.

What is thermoregulation in endothermic animals?

Endothermic animals maintain stable internal temperatures through metabolic processes.

What is thermoregulation in ectothermic animals?

Ectothermic animals rely on external environmental conditions to regulate body temperature.

What are the three types of skeletal systems?

Endoskeleton (internal), exoskeleton (external), hydrostatic skeleton (fluid-filled).

What is an open circulatory system?

Blood flows freely through body cavities.

What is a closed circulatory system?

Blood is confined to blood vessels and circulates continuously.