Diversity of organisms Flashcards
What is variation?
A key feature of living organisms, there’s variation between members of the same species and variation between different species (more variation if distantly related)
Morphological species concept vs biological species concept – problems with each?
Morphological species concept – comparison of outward form and inner structure (introduced by Carl von Linne) – problems like e.g. western and eastern meadowlark look the same but sing different songs so they never interbreed
Biological species concept – members of the same species interbreed and produce fertile offspring, through interbreeding they share genes in a common gene pool, traits remix each generation which prevents diverging of organisms into different species – problems:
1. Asexually reproducing species (e.g. blackberry offspring are clones)
2. Different species that naturally interbreed and produce fertile offspring (e.g. liger)
3. Fossils
4. Bacteria (horizontal gene transfer, regularly mate with other species – antibiotic resistance genes are transferred among bacteria that way)
Vertical vs horizontal gene transfer
Vertical gene transfer – from parents to offspring of the same species
Horizontal gene transfer – within the same generation but of different species
Steps of speciation:
- Populations of the same species are separated by barriers (geographical, biological, anatomical, reproductive (liger and lioness infertile offspring)
- Populations start to diverge due to different gene pools, habitat and different selection pressures = different diets, predators…
- The populations cannot interbreed
- Formation of new species (they don’t recognize each other as the same species)
Binomial naming system, species identification method
Universal name given to each discovered and described species (1st name is the genus name (capitalized) and the 2nd is the species name)
keys - identification systems used to identify an organism usually in the form of a book
Taxa – and specific taxa for humans:
Domain – Eukaria
Kingdom – Animalia
Phylum – Chordata
Class – Mammalia
Order – Primatae
Family – Hominidae
Genus – Homo
Species – sapiens
Why and how does classification into taxa constantly change?
e.g. the separation of Bacteria and Archea from prokaryotes – rRNA base sequence of various prokaryotes were compared, two very different groups of prokaryotes were identified and they are as different from each other as they are form eukaryotes
extremophiles
organisms that thrive in physically or geochemically extreme conditions that are detrimental to most life on Earth, like Archaea (thermophile, acidophile, halophile)
Cladistics, clades, parts of a cladogram
classifies organisms into groups based on their evolutionary relationships
groups of organisms that evolved from the same ancestor
root (common ancestor), terminal branch (from one node to another, extinct species), internal branch, node (speciation event) and derived trait
How is the level of relatedness estimated?
- Comparative morphology – comparing anatomical structure (not very relevant).
- Comparison of the chromosome number (species with more similar chromosome number are more closely related – not always accurate: grass > humans)
- Comparison of the base sequence of a gene or amino-acid sequence of a protein – sequence differences accumulate slowly and gradually but they accumulate at roughly constant rate, this can be used as an evolutionary (molecular) clock – the number of differences indicates how long ago the species have diverged from the common ancestor.
Estimation of the current species diversity
around 10 million (less than 6000 that have been discovered)
Definition of mass extinction, how many mass extinction events have happened thus far, about the most recent one
When three fourths of all species vanish,
Five mass extinction events have happened in the past and the sixth is underway - this is the only anthropogenic one
The most recent one was 66 million years ago - it was the result of a huge asteroid collision with the Earth which caused environmental disruption and the extinction of all non-avian dinosaurs - it allowed for the evolution of new species of birds and mammals
The sixth mass extinction is anthropogenic and includes the following species:
- Caribbean monk seal – lived in the Caribbean sea and western Atlantic, hasn’t been seen for over 70 years, it was hunted for its oil in the 18th and 19th century and starved due to overfishing of the coral reefs
- Giant moa – lived on the north island of New Zealand, hadn’t been seen since 15th century and it was hunted to extinction for meat
- Silphium – Libya, became extinct within a few hundred years of the arrival of ancient Greeks, harvested for use as a birth control agent and also became extinct due to overgrazing and desertification
Anthropogenic loss of ecosystem
Over the last 200 years we faced rapid loss of ecosystems due to human activity
e.g. mixed dipterocarp forests (deforestation due to urbanization and replacing of the natural forest with palm tree forests (imbalance in photosynthetic activity)) and Arial Sea loss (ecosystem collapses, biodiversity is lost)
Replacement of one with another ecosystem due to climate change (glacials, interglacals…) is a natural thing and it is very long and gradual and the nature can adapt – anthropogenic loss of ecosystems is very rapid and detrimental to biodiversity
How is species diversity evaluated
Using the range of species and the number of threatened species
Causes of the biodiversity crisis
- Overexploitation of natural resources (fuel wood, overhunting, mining and smelting)
- Global warming/climate change (anthropogenic)
- Introduction of invasive alien species to ecosystems
- Habitat destruction (overharvesting, agriculture, urbanization) – due to natural causes or anthropogenic
- Growing human population
- Pollution (leaching)
- Poor water management (e.g. Arial Sea loss), drying of wetlands
Approaches for the conservation of biodiversity:
- In situ conservation
- Management of nature reserves
- Rewilding
- Ex situ conservation
- Long term storage of germ plasm
