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Species & Species Diversity - Coggle Diagram
Species & Species Diversity
THE SPECIES PROBLEM
Cryptic Species
look the same but are of different species
they cannot interbreed to produce fertile offspring
Sexual Dimorphism
look different, but are of the same species
male and female of a species don't look alike
therefore it is difficult to define species - we cannot always rely on morphology to differentiate
almost 99% of all species that have ever existed are now extinct, many out of our knowledge
EXTANT : EXTINCT
1000 : 1
BIOLOGICAL SPECIES CONCEPT
Defines Species as:
A group of individuals that can interbreed to produce fertile offspring
species identification based on:
morphology, genetics, behaviour (but not always reliable)
the key to BSC - the group (one species) is reproductively isolated from other groups/species
Plus Points:
Intuitively simple and Logical
just involves the reproduction aspect
can or cannot interbreed
black and white
Based on the fundamental biological process of reproduction
not something subjective, it's very straight-forward
Allows us to recognise geographic variation (subspecies) to a degree but not necessarily leading to reproductive isolation
they can interbreed regardless of differences in genetics/morphology
Limitations
Assessment is subjective
heavily relies on how much we know about the species
can't draw conclusions until extensive research is done on the newer species
Don't cover asexual organisms
while there're so many of them
alternatives include:
phylogenetic cohesion
ecological
evolutionary
morphological
SPECIATION
Intro
Species have finite lifespans (e.g. mammals 1 mill years)
yet there's still an overall increase in diversity thanks to SPECIEATION
Speciation = emergence of new species (continuous process) which rely on genetic mutation and natural selection / selection of phenotype
Allopatric Speciation (other homeland)
organisms of an ancestral species evolve into 2 or more descendant species after many generations of physical separation causes by geographic barrier
Main factor that triggers speciation is not the geographical separation, but the distinctiveness of the 2 environments
abiotic and biotic factor take effect over many years
Changes:
adaptation to local environments
gene flow (% of different alleles in an area) leads to reproductive isolation
advantageous genes selected for subsequent generation due to natural selection
gene mutation may take place and even be selected
Sympatric Speciation (same homeland)
formation of 2 or more descendant species from a single ancestral species, all occupying the same geographic location.
Speciation due to preference or choices
Examples
one group of fruit flies prefer apple, other group prefers hawthorns. 2 groups evolve into 2 species with reproductive isolation because they have adapted to their specific habitats
both fruits have different flowering/fruiting seasons
different chemical content of fruits
Polyploidy in plants:
have more than 1 set of homologous chromosomes (e.g. 4N, 6N instead on 2N) because cells can't divide during Meiosis 1
they can't interbreed
e.g. 2N + 4N, gametes = 1N + 2N, offspring = 3N
offspring sterile because 3N cannot separate during meiosis (X 1.5N)
SPECIES DIVERSITY
number of species in an area and their relative abundance in an ecosystem (variation between species)
3 components of species diversity:
Species abundance
no. of individual species
Species richness
no. of different species in an area
Species eveness
how equal the abundances of the species are
specifically important for plants/producers in an area
reflects the dynamic within the community
food chains/ webs/ interactions/ responses
Why assess Species Diversity?
species-rich ecosystems are more likely to be stable and are able to buffer changes better
therefore will sustain the ecosystem better
changes won't have a huge effect on species-rich ecosystems
provide insights into the stability of the communities & ecosystem functions
functions as in nutrient cycling and energy flow (food webs)
identifying different species, learning their behaviours, reproduction and dynamics
we restrict humans' accessibility to those ecosystems to prevent disruptions
to asses the health of an ecosystem
health = balanced for a long time period, dynamic & sustainable
high biodiversity doesn't equal healthier ecosystem
biodiversity should be compares between same types of ecosystems
BIODIVERSITY
Intro
describes the enormous variety of life on Earth, and refers to everything living (plants, bacteria, animals and humans)
scientists have estimated that:
8 -15 million species of plants and animals in existence
only 15 being recorded and studied, but it's difficult to estimate as there're too many
only around 1.2 million species have been identified and most are insects
not all species are accessible for discovery
extreme weather, deep sea organisms etc.
millions of species remain a complete mystery
Importance of Biodiversity / Species Diversity
For Ecosystem
can better withstand changes and recover from variety of disasters (usually anthropogenic)
increased diversity = increased tolerance to damages and changes
therefore there will be better maintenance of ecosystems with each unique species doing their unique part
sustaining of ecosystem functions
For Living Organisms
species depend on each other (accept for autotrophs) especially in terms of food sources and services
increased diversity = increased variety of choices hence health
more choices enhance fitness and survival of the species
different variety = less likely to heavily depend on a single source
(e.g. koala & different eucalyptus trees)
For Human Beings
greater variety of crops and food, therefore increases human survival and likelihood
our health relies on diversity of our diet
we highly depend on ecosystem services to inhibit earth
air, water, climate stability, medical resources etc.
recreation and tourism (eco services) entertainment, fulfillment and mental wellbeing