Biodiversity and Cladistics

Species

A group of organisms that can successfully interbreed and produce fertile offspring

Variation =

defining feature of life

all species have variation

less variation within species than between different ones

Problems with species concept

• is it a pop or species?

• some organisms that we thought couldn't interbreed can when oppurtunity

• some orgs look similar but cant interbreed

• what about orgs that do asexual reproduction

• what about bacteria that shows horizontal gene transfer through plasmids

Binomial system for naming organisms

Genus species

second lowercase, first uppercase

always in italics

Diversity in chromosome numbers

• number is a fundamental species characteristic

• cant breed with orgs with different number

• can split/fuse to change number (rare and slow)

• most orgs diploid - number usually even

Karyotype

types of chromosomes of a species

Karyogram

images showing karyotype - sex and chromosomal differences can be seen

Steps of karyogram

• chromosomes most visible during mitosis (metaphase)

• cells stained and put on slide

• cells burst to spread chromosomes

• chromosomes arranged by: size, banding pattern, position of centromere

Genome

all the genetic material in an organism

unity and diversity of genomes WITHIN species

• gene = length of DNA 

• genes in species mostly the same

• differences can arise (alleles)

• there are positions in genes where different bases can exist called single nucleotide polymorphisms (SNPs)

• each individual has 4000-5000 SNPs

Diversity of eukaryotic genomes

• measured in base pains

• huge range 

• large genome does not equal lots of genes due to nonfunctional DNA

• Differences in base pairs show divergence between pops

• some genes don't show many differences due to vital function

whole genome sequencing

• human genome done in 2003

• started in 90s with simple organisms

• earth bio genome project: sequence all known species

• GOal of investigating evolutionary origins: protect biodiversity, fight disease, etc.

DNA barcodes

short sections of DNA distinct enough to ID species

• can ID from small piece of tissue in environment (collected from water, soil, etc.)

Dichotomous keys

• made to ID species within group

• numbered series of pair descriptions

• one clearly matches, other clearly wrong

• features must be easily visible

• each pair leads to another pair/id

What is the need for classification

helps with identifying, organizing knowledge, and making predictions

How was classification done previously

• based on mophological criteria (internal and external parts)

• Hierarchical order (class, order, family…)

• difficult to tell when to separate

New classification

• based on evolutionary relationships/clases 

• shared traits from common ancestor so can pake predictions:

  • will new daffodil species also secrete substance to treat Alzheimer's 

  • new bats also have four chamber hearts and hair

clade

group of orgs evolved from common ancestor

• living and extinct members

• use biochemical evidence to determine (DNA/aa sequences)

• smaller clades nested in larger 

Paradign shift

• some traditional taxa still used but clades now more common

• wolf and palm by unranked clades

gradual accumulation of species differences

• differences in genes accumulate

• we can estimate the time a species diverged based on the number of differences between them

• ex: humans split around 4.5 million years ago based on calcs

How are cladograms done

• uses base sequences of genes or amino acid sequences of proteins

• differences used to calculate time diverged

• use principle of parsimony

principle of parsimony

the simplest solution is the most likely (lowest number of sequence changes)

Parts of cladogram

• terminal branches = individual clades

• branching points = nodes

• root = base of cladogram

• branching pattern assumed to match phylogeny of species

example of reclassification from cladistics

figwort family 

• originally 5000+ species

• used chloroplast DNA to investigate

• major reclassification 

  • 2 families were merged with it

  • 2 moved to new family

  • 25 to other existing families

also mustelidae family: weasels, badgers, otters

The three levels of biodiversity 

• ecosystem diversity = variety of the combinations of species living together in communities) due to geographical ranges and varied environments on earth)

• species diversity = the many different s species on earth (different body plans, nutrition mores, life cycles, etc.)

• genetic diversity within a species = variety in gene pool 

  • lower number of organisms =  decrease in genetic diversity = increase in inbreeding

Mass extinctions

• 5 mass extinctions

• asteroid that killed dinosaurs 

• previous four caused by volcanic activity or atmospheric/climate changes 

Causes of anthropogenic species extinction

• over-harvesting

• habitat destruction 

• invasive species

• pollution

• Global climate change 

Giant Moas

• 3.6 meters tall

• took less than 200 years to be hunted to extinction

• native to new zealand

atitlan grebe

• was flightless

• blac bass introduced to habitat to increase tourism

  • resource competition and ate chicks

• tried to save but earthquake destroyed refugee zone

Mount glorious torrent frog

• amphibians spend most of their time on land so are vulnerable to species destruction

• lives in rainforests in australia

• 10,000 hectacres of trees cleares

  • changed water flow and turbidity disrupting breeding

• alien feral pigs

  • contaminated water with mud

  • ate frogs

• also invasive plant species and infection enytrid fungal disease

Causes of ecosystem loss

• land use change for agricultural expansion

• urbanization

• overexploitation of natural resources

• mining and smelting = land use change = destruction and also pollution

• building dams and irrigation = loss of aquatic ecosystems

• drainage/diversion of water = loss of wetlands

• leaching = eutrophication = algae blooms

• climate change = animals not adapted to change

examples of ecosystem loss

• mixed dpterocarp forest in asia

  • mdf mostly logged or palm oil plantations

  • mainly in areas overlying peat = co2 released during drainage for land conversion = increase in global temps = increase in sea level = destruction of mdf

• loss of aral sea

  • rivers that fed lake were diverted = falling water levels

  • also increase in salinity = species extinction

Evidence for biodiversity crisis

• population size

• monitor range of species

• diversity of species in ecosystem

• “richness” and “evenness” of biodiversity stats

• number of threaded species within a taxonomic group

• genetic diversity within species

Causes of biodiversity crisis

• hunting and overexploitation of resources

• urbanization

• deforestation and land clearance

• pollution

• spread of invasive species

Human population growth

• 1700-2000 steady increase

  • sharp increase in rate after 1950s

• 2000-2100

  • pop will double

  • rate will plateau after 2050

Approaches to conservation

• in situ = conserve species in there natural habitat

• ex situ = preservation of species outside their natural habitat

• germplasm = storing seeds and tissue samples

• all methods necessary to conserve biodiversity

Indentifying endangered animals

• EDGE of existence criteria: 

  • few or no close relatives - member of small clade?

  • in danger of extinction because all remaining populations threatened?