Bio 202: Evolution and the origin of Species

Exam 1 powerpoint chapter 18

What are three observations that support evolution?

1. Organisms are suited to their environments

2. Many characteristics are shared amongst organisms (living space, body parts)

3. Life is Diverse, they all use DNA

What molecule is used by all living organisms?

DNA

What is paleontology?

The study of fossils, remains of traces of dead organisms

What did Plato believe about species?

Species are unchanging; part of a fixed natural scale.

What is catastrophism?

Theory by Georges Cuvier: environmental catastrophes affect species but don’t change them.

What is uniformitarianism?

Geological processes are constant over time,earth is older than previously thought

What was Lamarck’s hypothesis

Traits acquired during an organism's lifetime can be inherited.

What is natural selection?

Heritable traits that improve survival and reproduction become more common in a population

What is adaptation

Traits that enhance survival and reproduction

What types of evidence support evolution?

Fossils, homologies, vestigial structures, genetic similarities

What are vestigial structures?

Body parts that have lost their function through evolution

What are convergent evolution?

Unrelated species independently evolve similar traits

Is evolution “just a theory”

No- it’s a scientific theory supported by evidence

Do individuals evolve?

No- populations do.

Is evolution goal directed?

No- it is not driven by a specific goal

What is biological Species Concept?

Species are groups of interbreeding natural populations that are reproductively isolated

What are limitations of the Biological Species Concept?

Does not apply to fossil or asexual organisms; gene flow may occur between distinct species

What is the morphological species concept

Defines species based on physical traits like shape, size, and structure

What are strengths of the morphological species concept?

Useful for fossils and extinct species

Doesn’t require knowledge on reproduction

What are limitations of the morphological species concept?

Subjective: traits can vary within species

Cryptic: species can look similar but be genetically different

What is ecological species concept?

Defines species based on their ecological niche, how they interact with the environment

What are strengths of ecological species concept?

Usefull for organisms that reproduce asexually

emphasis on role in ecosystem and resource use

What is Phylogenetic species concept?

It defines species as the smallest group of individuals sharing a common ancestor, forming on the tree of life

What are strengths of Phylogenetic species concept?

Based on genetic data and evolutionary history

can identify cryptic species

What are weaknesses of Phylogenetic species concept?

Requires extensive genetic analysis]may lead to splitting species into many small groups

What are the key observations that lead to natural selection?

1. Variation: Individuals in a population vary in their heritable traits.
2. Overproduction: More offspring are produced than can survive.
3. Competition: Individuals compete for limited resources.
4. Differential Survival/Reproduction: Individuals with traits better suited to their environment tend to survive and reproduce more.

What is speciation?

The process by which one species splits into two or more distinct species.

What is Allopatric Speciation?

Speciation that occurs due to geographic isolation between populations.

What is Sympatric Speciation?

Speciation that occurs without geographic separation, often due to genetic changes, habitat differentiation, or sexual selection.

What is Reproductive Isolation?

Biological barriers that prevent different species from producing fertile offspring.

What are Prezygotic Barriers?

Barriers that prevent mating or fertilization (e.g., behavioral, temporal, mechanical isolation).

What are Postzygotic Barriers?

Barriers that occur after fertilization, leading to inviable or sterile offspring.

What is a Hybrid Zone?

A geographic area where members of different species meet and mate, producing offspring of mixed ancestry.

What is Reinforcement in a hybrid zone?

When hybrids are less fit, natural selection strengthens reproductive barriers.

What is Fusion in a hybrid zone?

When reproductive barriers weaken and two species merge into one.

What is Stability?

When hybrids continue to be produced, perhaps because they survive or reproduce better than parent species in certain regions, leading to a stable but narrow hybrid zone.

What are homologies?

Similarities between species that result from a shared ancestry.

What is Vicariance?

A form of allopatric speciation where a population is split by a physical barrier (e.g., mountain range, river).

What is Dispersal?

A form of allopatric speciation where a few individuals migrate to a new area and become isolated.

What is Adaptive Radiation?

Rapid diversification of a single lineage into multiple species, each adapted to a different ecological niche.

What is Polyploidy?

A genetic mutation resulting in extra sets of chromosomes; can lead to instant speciation, especially in plants.

What is Habitat Differentiation?

When populations in the same area begin to exploit different resources or niches, leading to reproductive isolation.

What is Sexual Selection?

A form of natural selection where mate choice drives the evolution of traits (e.g., bright plumage, mating dances).

What is a Gene Pool?

The total collection of genes and alleles in a population.

What is Allele Frequency?

How common a particular allele is in the gene pool.

What is Genetic Variation?

Differences in DNA among individuals; the raw material for evolution.

What is a Mutation?

A change in DNA sequence; can introduce new alleles into a population.

What is Genetic Drift?

Random changes in allele frequencies, especially in small populations.

What is Gene Flow?

Movement of alleles between populations through migration.

What is the Founder Effect?

Genetic drift that occurs when a small group starts a new population.

What is the Bottleneck Effect?

A sharp reduction in population size that alters allele frequencies.

What is Cladogenesis?

Branching evolution where a species splits into two or more.

What is Anagenesis?

Evolution within a single lineage without branching.

What is a Monophyletic Group?

A group that includes a common ancestor and all its descendants.

What is a Paraphyletic Group?

Includes a common ancestor but not all descendants.

What is a Polyphyletic Group?

Grouped species without a common ancestor—based on traits, not lineage.