Evolution & Biodiversity (A4.1-A4.2)

Evolution

Evolution

change in the heritable characteristics of a population over time

Darwin’s Theory

variation exists → nature selects the indivisual with the traits best adapted for survival and reproduction = evolution over time

supoorted by genetics (variation is present in a pop due to the precesne of alleles)

evidence for evolution

Biomolecules, selective breeding, homologous structures and analogous structures

Biomolecules (genetic variation)

same genes are present in organisms which have evolved from a common ancestor. differences in the base sequences of DNA (+RNA n protein) are the result of mutations

closley related species have very similar gene and protein sequences as there will be a samll # of mutations as they diverged from a common ancestor.

Selective breeding

process of choosing animals/plants with desirable traits to breed together and produce offspring with more of those desirable traits

selective breeding e.g: (woof)

Canius lupus - selectively bred them with desirable traits to create the variety of dog breeds we have today (sled dogs)

selective breeding e.g: plant

Brassica oleracea (demonstrates how fast evolution can occur) selective breeding results in changes to the heritable characteristics of oraganisms

turned into cabbage, kale and brussell sprouts

Homologous structures

body parts of different organisms that are similar in structures but different in function

present in organisms that have descended from a common ancestor as a result of evolution (more similar the structure, the more recent common ancestor)

homologous structures e.g.

PENTADACTYL LIMB: humans, dogs, birds, whales with pentadactyl limbs have evolved from a common ancestor

structure is similar, function is modified: (humans-writing, dogs-running, birds-flying, whales-swimming)

Convergent evolution

evolution of similar structures in species NOT RELATED due to a recent common ancestor

Analogous structures

have common function but do not share a common ancestor (evolved by convergent evolution)

Analogous structure e.g.

WINGS: in all 3 groups have the same function (flight), none of the groups of organisms share a common ansector with wings so each one evolved independently

Homologous vs. Analogous

Homologous: from a common ancestor, similar structure, different function (pentadactyl)

Analogous: not from common ancestor, similar function, differing structure (wings)

Speciation

only occurs if a population of a species is reproductively isolated and no longer able to reproduce w/ original pop

occurs as pre-existing species evolve into new species over time

gradual evolution DOES NOT = speciation

Extinciton

occurs when there are no living memeber of a species remaining

speciation increases total # of species on earth, extinction decreases it

Reproductive isolation

when there is a barrier whioch prevents indivisuals from reproducing (fertile offspring)

result of geographical isolation

Geographical isolation

when 2 pops. of the same species are prevented from reproducing due to geographical features → rivers, mountains, different islands

e.g. for reproductive n geographic isolation

CHIMPS & BONOBOS: pop of apes lived in central africa, the pop became geographically isolated into 2 distinct pop as the congo became wider. the 2 pops then became reproductivley isolated as members of each pop were unable to reproduce together.

Selection pressures: different traits were selected to better aid their survival on either side of the river

boring bonobos - more vegetables no competition, aggressive chimps - had to fight gorillas and more meat

Biodiversity (definition)

variety of living organisms (plants, animals, micro-organisms) on earth

genetic diversity (definition)

diversity seen in genes (alleles) within a population of species

species diversity (definition)

#and type of oraganisims that existed during a specific amount of time

ecosystem diversity deinition

variety of ecosystems in a given area

MOAS - case study

flightless birds, native to new zealand

fossil records indicate the polynesians used the birds as a food source (over exploitation), within 100 years birds were hunted to extinction

diseases brought by humans could also be a factor

Caribean Monk Seal

marine mammals found in the carribean sea, fishermans killed 100s of seals every night (fuel lamps, grease machinery)

less thar 600 years the sealsbecame extinct, overfishing in their areaas meant these animals felkl short of food sources like fish (starved to deaath)

Splendid Poison Frog

were trafficked as part of the “pet trade”

outbreak of a fungal disease

habitat was reduced due to logging, conversion of forests for agriculture and expansion of urban areas

Anthropogenic Species Extinction

6th mass extinciton, result of human activity: habitat loss/destruction, exploitation, climate change, invasive species

Tasmanian Wolf case study

INVASIVE SPECIES, OVEREXPLOITATION

large carnivores in Tasmania, colonization by europeans ead to a decrease of an already low pop

europeans offered rewards for killing them as they hunted for fish

dingoes introduced byt the euro’s out competed the wolves

kept as pets or zoos

Ecosystem services

• supplying recources → water, food, timber and medicine

• provides basic services essential for survival:

  • decomposition of waste, storage of carbon, climate regulation, water cycle

Ecosystem Loss

human activity has lead to the destruction and decline of ecosystems

when entire species collapse the species dependant on the ecosystems are driven to the brink of extinction

Fall of Dipterocarp Forests

southeast asia there are tropical rainforests

key stone species (important)

• food sources (leaves, fruits, seeds)

• provide homes

• roots hold soil

• decomposition of leaves enriches soil

• help fight climate change → store and lock co2

under threat by logging, deforestation

the destruction of these forests + already endangered animals to become more vulnerable

Dying Reefs: case study

reefs are one of the earth’s most diverse ecosystems

• benefits:

  • sustaion food webs

  • sources for new medicine

  • protect coastlines from erosion and storms

  • provide food for animals and humans

• threats:

  • pollution - oil spills, plastic

  • destructive fishing activities - overfishing

  • unsustainable tourisim - divers damaging them

  • climate change- rising ocean temp leads to ocean acidification, leading to coral bleaching

Population Explosion

in 200 years it went from 1 billion to 7 billion

as the pop grows, the demand for food, water and space increases

• increase pressure leads to over exploitatation of natural rescources and habitat destruction = impacting biodiversity

Hunting & overexploitation

decrease and even extinction of many species

poaching and habitat destruction

countries try to have policies but illeagal poaching still continues

Destruction of Habitats

as the demand for space increases more and more natural habitats are lost

when habitats are changed drastically, species cannot adapt as fast and can no longer survive

Habitat Fragmentation

urbanisation invades on existiing natural habitats and can fragment them into smaller habitats

• E.G.

  • laying of railroads thru a natural habitat makes the area smalller and isolates patches

  • restricts animal mobility - reduces access to food and increases risk of extinction

  • SOLUTION: building safe passages for animals

Invasive Species

as humans took over the earth they introduced new species accidentally or on purpose

• these species become invasive species

• sirupt exisiting food chains, reproduce food chains

• spread aggresivley and outcompete the native species

includes plants, animals and microorgansims

Pests and Diseases

global transport has also introduced pests/diseases to native species

global trade in amphibians has led to fungal disease (decrease in pop)

Pollution

leading cause of biodiversity

• plastic in oceans is often ingested by marine animals, affecting consumers

• dumping of garbage pollutes ocean, also becomes breeding ground for pests

• the release of sulfur dioxide and NO2 from industries results in acid rain - detrimental effect on plant and animals

In-situ conservation

way of conserving animals and plants in their natural habitats maintaing the original biodiversity of the area

involves designating, managing and maintaining areas for the protection of the and animals.

less disruptive & cost-efficient

E.g

• national parks, wildlife sanctuaries, and marine reserves

• allows the species to continue living in the habitat to which they are adapted to - preserves their natural behaviout and revents diruption in the food chain

Ex-situ conservation

plants and animals are conserved OUTSIDE their natural habitats

E.g:

• zoos, aquarimes, botanical gardens

• sometimes the # are too small to sustain the species or the risk of poaching is high

  • scientists establish gene banks to store biodiversity + storage of GERMPLASM

Captive breeding

conservation technique for preventiing the extinction of species whoose populations are small and on the verge of extinction

animals in zoos are encouraged to breed and then reintroduced into the wild

• ONE DRAWBACK is small pops already have low genetic diversity so the chances of passing unfit genes increases

e.G

• Arabian Ox - became extinct in the wild, the antelopes that were in zoos were “trained” for realse and ensured that the species could be realse back into the wild

Rewilding

conservation technique which allows wildlife and natural processes to reclaim areas bringing back biodiversity

• habitat is rrestored to what it would have been if humans did not interfeer

plants and animals that have dissapered from the habitat are reintroduced (help build ecosystems)

Reclamation of degraded ecosystems

unsustainable human activity often causes degradation of land and water - loss could be due to erosion of soil, deforestation, salination

land restoration strategies recover and realim degraded ecosystems

• help from local communitites and indigenous peoples yeild higher result as they have deep knowledge of the land

• EDGE: helps endangered animals, ED - evolutionary distinctivness, GE - globally endangered

Living PLanet Index

measure of the average decline in monitored wildlife populations