EXAM 2 BIO

Species Plot

Showing variation within and between species

Speciation

A splitting event that creates two or more distinct species from an ancestral species

Species concepts

morphological

biological

phylogenetic

ecological

Morphological concept definition

Species are defined by shared observable physical traits

organisms that look consistently different are considered different species.

Morphological concept strengths

can be simple and practical

useful for fossils and preserved specimens

helpful for rapid field identification

Morphological concept Limits

can miss cryptic species

can miss polymorphic species

convergent evolution can make unrelated species look similar

Cryptic species

species that look the same but are different

polymorphic species

species that look different but are the same

convergent evolution

unrelated groups evolve to look or function similarly

Biological concept definition

species are groups of actually or potentially interbreeding natural populations

they are reproductively isolated from other such groups

Biological concept strengths

connects species to gene flow and reproductive isolation

closely tied to the process of speciation

biological concept limits

not useful for fossils

does not work well for asexual organisms

hard to apply to geographically isolated populations

hybridization can blur boundaries

BSC reproductive isolation barriers

prezygotic

postzygotic

Prezygotic isolation

temporal- breeding occurs at different times

habitat- breeding occurs at different habitats

behavioral- different courtship behaviors

gamete- egg and sperm are not compatible

mechanical- reproductive structure aren’t compatible

postzygotic

hybrid viability- offspring do not develop normally resulting in high mortality

hybrid sterility- offspring can not reproduce

phylogenetic concept definition

the smallest diagnosable evolutionary lineage

members share a common ancestor and unique derived traits

phylogenetic concept strengths

uses evolutionary history

can detect cryptic species

works well with DNA data

based on testable criteria

phylogenetic concept weaknesses

requires strong phylogenetic data and sampling

different analyses can give different boundaries

may split populations into many small species

does not apply to fossils

PSC monophyly and synapomorphies

monophyletic group: an ancestral population and all descendants

synapomorphy: a trait unique to a monophyletic group

PSC Monphyletic groups

phylogenetic species: smallest monophyletic groups

Ecological concept definition

a species is defines by its ecological niches/role

populations using different resources or habitats may be different species

Ecological concept strengths

links species to adaptation and ecology

useful when niche differences are biologically important

ecological concept limits

niches can overlap or change over time

hard to measure a niche completely

not all species are clearly seperated ecologically

ESC adaptive radiation

evolutionary process where a single ancestorial species rapidly diversifies into multiple new species, each adapting to fill different ecological niches in a given geographical area

Speciation key process under BSC

reduced gene flow → genetic divergence → reproductive barriers → reproductive isolation → seperate species

Allopatric speciation

speciation by geographic isolation

Types of Allopatric speciation

vicariance

dispersal/ founders’ effect

peripatric speciation

Vicariance

a previously continuous population is split by a geographic barrier

dispersal/founders effect

a small group moves to a new isolated location and becomes separate from the original population

peripatric speciation

a small population at the end of the species range becomes geographically isolated

Sympatric speciation

Speciation without geographic isolation

- disruptive selection

-polyploidization

Adaptive radiation

a single lineage rapidly produces many descendants species with a wide range of adaptive forms

Why adaptive radiation?

ecological opportunity

• availability for different kinds of resources or more of them

Vacant niches

trait innovation

• evolution of a key trait that allowed descendants to live in new areas or exploit new resources

Systematics

The scientific studies of the diversity of organisms and their evolutionary relationship through time

Taxonomy

names and describes organisms and place in hierarchical system

Phylogenetics

constructing hypothesis of evolutionary relationships among living and extinct forms of life.

Traits including

morphological (Physical traits; fossils)

molecular (DNA, RNA, Protein sequences)

Behavioral (Mating rituals, migration patterns)

Ecological (biochemical pathways, metabolic abilities, temperature tolerance)

Homology

similarity shared from ancestry

homoplasy

Similatiry that evolved independently or reappeared due to reversal.

Homoplasy:covergent

similar traits evolve independently in distantly related groups

Homoplasy: Parallel evolution

Similar traits evolve independently in closely related groups

Homoplasy reversal

a derived trait returns to an ancestral-like state

Ancestral traits (pleiomorphies)

Inherited from a distant common ancestor. they do not help group closely related subsets withing a larger group

Shared derived traits (synapomorphies)

Unique features shared by a specific clade (a group with a common ancestor and all its descendants) These are the primary traits used to build evolutionary branches

monophyletic Groups

Nodes=ancestor

terminal node=taxonomic group

monophyletic=group containing ancestor and all the descendants

monophyly=clade

Paraphyletic

group containing the common ancestor and some but not all of the descendants

polyphyletic

group without the most recent common ancestor

Sister groups

two groups that are more closely related to each other than either is to anything else on the tree

Fossil

preserved remains, impressions, or traces of an organism that lived in the geological past

remains

bones, teeth, shells, or other stuctures.

impressions

imprints of leaves, shells, or other structures.

traces

evidence of an organism’s activity, such as footprints, burrows, or fossilized feces.

What can fossils tell us?

fossils provide evidence of past life

fossils help us reconstruct evolutionary history

why is the fossil record incomplete

preservation is selective

discovery and sampling are uneven

what does this mean for our interpretations

Relative dating: aging fossils

superposition places fossils in sequence when sedimentary layers are undisturbed

numerical dating: aging fossils

radioactive isotope decay dates suitable rocks and minerals

tempo: question

how does morphology change through geographical time

diversification: question

how does morphology diversify when in the presence of ecological diversity

extinction: question

how does species loss alter biodiversity

tempo: gradualism

morphological changes accumulate relatively gradually through time

tempo: stasis

little net morphological change across an extended interval.

tempo: punctuated equilibrium

long intervals of stasis interrupted by relatively rapid morphological change associated with speciation.

Diversification

adaptive radiation

colonization of environments with available niches

mass extinction

evolutionary innovation that makes new available resources

Extinction and diversification

Biodiversity changes as new lineages originate and old existing ones disappear

diversification is not automatic

Background extinction

ongoing species losses between major extinction crises.

Mass extinction

unusually widespread species loss during a short geological interval.

Prokaryote

Cells that lack a nucleus

Nutrient cycling

Decompose organic matter and recycle carbon, nitrogen, and other nutrients.

Primary production

Cyanobacteria photosynthesize and helped oxygenate Earth’s atmosphere

symbiosis

Support plants and animals

evolutionary history

An ancient bacterial endosymbiont gave rise to mitochondria; cyanobacteria gave rise to chloroplasts.

human health

Many are beneficial; some cause disease and shape the evolution of host defenses.

Biotechnology

Used to produce foods, medicines (including insulin), and tools for genetic research.

Small cell size

High surface-area-to-volume ratio facilitates exchange with the environment.

prokaryotic organization

No nucleus or typical eukaryotic membrane-bound organelles

specialized structure

Support cell shape, movement, reproduction, and other essential functions

functional diversity

Bacteria occupy many environments and carry out a wide range of biological processes

cytoplasm

all contents of a cell excluding nucleus in eukaryotes

cytosol- fluid in cytoplasm

chromosome

single and circular

nucleoid

region of cell where the chromosome is located but not separated by a cell membrane

plasmids

small DNA molecules separated from bacterial chromosome

carry gene for specialized traits

some can transfer between bacteria cells

ribosome

made of RNA and proteins

site for manufacturing proteins

small subunit reads RNA

Large units makes proteins

Other internal structures

photosynthetic membrane

cytoskeleton

cell membrane

cell wall

Polymer of sugars and amino acids called
peptidoglycan

Helps keep shape

Resist osmotic stress

Archaea vs bacteria

Archaea-isoprenoid tail

bacteria-fatty acid tail

Gram positive

purple stain

thick cell wall

no outer membrane

plasma membrane

often susceptible to antibiotic targeting cell wall

gram negative

pink stain color

thin cell wall

has outer and plasma membrane

outer membrane has additional barrier to antibiotic

Gram Staining and Evolutionary Relationships

Bacteria with the same Gram stain result are not necessarily close relative

Gram-positive and Gram-negative bacteria are
not two monophyletic groups.

Flagellum

molecular motor,

Fimbriae

Adhere to surface

pilus

exchange of genetic information

Binary Fission

DNA is copied, and protein filaments attach →DNA copies are separated; ring of protein forms → Ring of protein draws in membrane → Fission complete

Binary fission product

two daughter cells from one parent cell.

vertical inheritance

Mutations in DNA passed from parent to offspring

Horizontal inheritance

New DNA acquired from another organism without reproduction.

Three mechanisms of horizontal gene transfer

transformation

transduction

conjugation

transformation

uptake of DNA from the environment

transduction

A virus transfers bacterial DNA

Conjugation

DNA is transferred through direct cell to cell contact