ESS W1 L1 p2 - biosphere

part 2 - biodiversity - life on earth

what is biodiversity

    ‘variability among living organisms from all sources including inter alia terrestrial, marine and other aquatic organism and the ecological complexes of which they are part; this includes diversity within species, between species, and of ecosystems’ – UN convention 1992

biodiversity - within a species

genetic variation – individuals of the same species are not all identical

biodiversity -between species

variety of different species on same habitat

biodiversity -between ecosystems

ecosystem variation – different environments support different kinds of life

Global biodiversity:

• On a global scale diversity isn’t uniform

Species biodiversity:

• 8.7 mil eukaryotic organisms catalogued so far

• 86% existing specie son earth (terrestrial) and 91% species in ocean still await description – more at al 2011

• Habitats still need exploring

• Different ways we define species – advancements on DNA analysis helping

• Small stuff 0 difficult to detect

• Changing methods and technology – human id vs. DNA analysis

Microbial diversity

•   ‘100 mil times as many bacteria in the oceans (12 x 10^28) as there are stars in the known universe’  - microbiology by numbers

• Bacteria been around for biliions years – oldest and most biodiverse group/ kingdom, followed by archaea and fungi

• Estimated 3 mil – 1 tril estimated living organisms– difficult to know

Biodiversity loss:

•   Estimated 130 animals and plant species go extinct every day – Vitorino and Bessa 2018

• A huge global challenge mainly driven by human activity

• Biodiversity needed for healthy ecosystem

•   E.g. flying insects declined 60% in 20 years

•   Important for food chains

• Pollution, deforestation, over fishing, industrial scale farming, urban landscapes, human induced climate change drives wildfires and makes parts of the world uninhabitable for some species as our climate warms

Evolution:

• Persistence of bacteria over time

• All species evolved from a single ancestor

• All linked together via evolutionary tree – tree of life

genetic variation

• Differences between organisms caused by differences in DNA

•   A gene is the basic unit by which characteristics are passed from generation to the next

• Slightly different forms of a gene (mutation) called an allele

• Evolution = change in genetic material (genotype) of a population or organisms across generations

• Change in an organism’s appearance (phenotype) is influenced by genetics and environment

• When an allele persist in a population – the trait gets passed down from one generation to the next – this is when evolution occurs

Genotype vs phenotypes: example

• Peppered moth – biston betularia

• Get two phenotypes

• Require camo against pred birds

• Light pheno – thrive in non-polluted areas – disguised by lichen on trees

• Dark pheno – thrives in polluted areas, where sulphur kills lichen on trees

• Related to the environment

• Uk – industrial revolution – influences persistence of dark phenotype

• From 1% to 90% of population

Natural selection:

• Charles Darwin – on the origins of species 1859

• Natural selection

• A process in which individual organisms that possess more favourable charactertics are more likely to survive and reproduce

• Operates by challenges in allele frequencies (genetics not understood at the time)

• Environment a driving factor for evolution

Speciation:

• Evolutionary process by which reproductively isolated biological populations evolve to become distinct species

• Isolation:

  • Physical isolation (geographical processes)

  • Reproductive isolation (mutation changes)

  •   Results in significant changes in genetics that means the isolated group can no longer reproduce with the original population

•   Leads to new forms of life and biodiversity

What is a species:

• Biological species concept:

  • Species are groups of interbreeding natural populations that are reproductively isolated from other groups

 

Geography involved in speciation:

• So explains species diversity and distribution

•   Biodiversity not equally distributed across the planet. Tropical regions – highest number of different species (of vascular plants) and species vary across the planet

speciation

process of a single lineage splitting into two or more daughter lineages. When populations are spatially isolated, they no longer exchange genes and can diverge

Geographical isolation: allopatric speciation

• new sub population evolve due to geographic separation e.g. formation of a mountain range or tectonic plate movement

• one population of living organisms become subdivided in two separate subpopulations due to a geographical boundary between them.

• The two subpopulations stop interbreeding and thus new mutations can not be exchanged for generations. This leads to appearance of new and different variations in the two subpopulations, and the isolated subpopulation eventually fails to interbreed with the parental population (even when the barrier is removed) giving rise to a new species.

Geographical isolation: vicariance

• physical splitting of populations

• Isolation causes genetic divergence, so plays a key role in speciation.

• we can imagine examples e.g. movement of continents, mountain formation, volcanic island formation (and dispersal to them with subsequent isolation), SLC

• differences in the local conditions in the two land bodies may then result in adaptation to those settings and the development of new species

• so geographic isolation, breading amongst separated groups resulting in genetic divergence, which then leads to reproductive isolation

• this separation by geographic barriers resulting in new species from an original group is known as vicariance

Geographic Isolation

• leads to genetic divergence.

• e.g. one species split by the rise in a mountain range- new genotypes will appear in the separate populations,

sympatric speciation

evolution of new species from an ancestral species, while both inhabit the same geographic region.

variation types

Plate tectonics:

• Driver of  speciation

• Splitting of Pangea (200 ma) caused isolation, in turn speciation

• But a lot of species diversity happened in last 60 ma

• But doesn’t explain all biodiversity

Geological processes and biological evolution:

• Formation of mountain ranges – e.g. south America has led to biodiversity hot spots

• Volcanic activity has formed new islands, creating new habitats

• Species have adapted to these environments and evolved in situ and are endemic (unique) to these places

Climate change and evolution:

• Climate change has driven evolution too

•   ‘successive climate crises in the deep past drove the evolution and radiation (diversity) of reptiles’

• Correlation between morphological features of species and climate

• Individual species may adapt to environmental changes or disperse to new locations