ENV1800 Biodiversity and Food Webs

Define biodiversity and what it refers to

Variety of life on Earth, variability within species, between species, and ecosystems

• No. of species living in an area

• Variety of different ecosystems in an area or variation within one type of ecosystem

• Variation of genes within a species

Biological classification

A way of sorting and grouping living things to study them carefully and understand relationships aka taxanomy

Taxanomy: The scientific process of organising into hierarchical systems based on shared characteristics and evolutionary relationship

Purpose of biological classification

• organisation - structured

• identification - name-based on unique feature

• relationship - evolutionary connections through shared ancestory

List the order of the biological classification

Broad to more specific

1. Kingdom - Animalia

2. Phylum - Chordata (has back bone)

3. Class - Mammalia (warm-blooded)

4. Order - Carnivora (eats meat)

5. Family - Felidae (Big cats)

6. Genus - Panthera

7. Species - Panthera tigris jacksoni

Kindly Put Candy Out For Good Students

What is placed above kingdom?

Domain

• Archaea

• Bacteria

• Eukaryotes - has nucleus and houses the seven biological classifications

Bacteria and archaea are prokaryotes lack nucleus and membrane bound organelles

What is the class for birds and name one family

Aves

• strong backbone to fly

Sturnidae

• plumage dark and glossy

Largest order for birds and name 2 others

Passeriformes

• 3 toes forward and one backwards

• help them perch on trees

Coraciiformes

• colourful birds e.g kingfisher

• Syndactyl - 3 toes point forward and 3 4 fused at the base

Bucerotiformes

Why are the scientific names important?

Common names may differ from places

Scientific names in latin are universally used and allow scientist to identify them accurately

Key processes which regulate number of species

1. Speciation - the evolutionary process by which populations evolve to become separate species
   - Physical barriers and different environments
   
   

2. Extinction - the irreversible process where a species or distinct biological population forever ceases to exist
   - Naturally —> Tragic event
   - Hunting
   
   

What are species

• Interbreeding populations to produce fertile offspring

• Reproductively isolated from other groups

Isolation of populations within a species creates 2 separate populations prevent mix of gene pool through sexual reproduction

Population evolve different traits overtime due to

1. Natural selection - different environmental conditions favour different traits FOR SURVIVAL environmental pressure
   
   

2. Sexual selection - females are more likely to mate with males that display distinctive traits
   - dont pick because the male has traits for survival
   - higher chance of reproducing
   
   

3. Genetic drift - change of the frequency of traits in a population by RANDOM chance
   - chance events such as storms or typhoon

Even though they evolved from the same species, after speciation when they meet again what may happen?

• no longer able to recognize to breed

• breed but do not produce fertile offspring

3 ways to define a species based on different classification

Biological Species Concept (BSC)

• a group of interbreeding organisms that produce fertile offspring

• not applicable to bacteria/extinct species

• explain cryptic species

Morphological Species Concept (MSC)

• a group of organisms with similar anatomy

• physical traits

Genetic Species Concept (GSC)

• a group of genetically compatible interbreeding natural population that is genetically isolated from other such groups

• look at DNA

Biological Species Concept (BSC) and Limitations

According to BSC a species is

• a group of interbreeding organisms that produce fertile offspring

• explain cryptic species - species that look almost identical but are not the same

Limitations

• Not applicable to bacteria/extinct species that reproduce without mating asexual

• Bacteria mate through binary fission so cannot

Morphological Species Concept (MSC)

A species to MSC is

• a group of organisms with similar anatomy

• physical traits

Useful when

• identifying species without capturing

• identifying species in fossil records (dinosaurs)

Limitations

• Hard to apply to cryptic series but genetically different

• Arguments between scientists

Genetic Species Concept (GSC)

A species is

• a group of genetically compatible, interbreeding natural population that is genetically isolated from other such groups
  
  

uses DNA barcoding a method of species identification that uses a short, standardized DNA sequence a barcode to identify an organism - sequencing a short randomized DNA

Importance

• Reveal genetic differences not visible to the naked eye

• detect cryptic species that morphological species concept might miss

• Works for all types of organisms including asexual species

• Can be applied to small tissue samples or even environmental DNA (EDNA from soil or water)
  
  

Limitations

• Require expensive labratory equipment and expertise

• Expensive and time consuming

How much genetic difference is enough to classify a new species?

Typically 98.7% genetic similarity is considered the same species in the barcode region

• can vary

Most common species concepts used are

Morphological and Genetic Species Concept

MSC

• identify based on physical and anatomical traits (colour, shape)

• practical for field work and fossil records where genes cannot be obtained

• however limiting especially for beetles where they all look similar

GSC

• detect subtle differences in the gene

• identify cryptic species

Describing a new species

Share with community, to ensure introduced species is recognized and properly documented for future research

• Publish a written description with pictures
  - Include pictures of closely related species to highlight what makes the species different
  - species unique morphology - distinguishing feature
  - high quality
  - submit to peer review journal
  
  

• A type specimen or holotype example of the new species is placed in a permanant location for researchers to look at
  - Gold standard reference for identification
  
  

• Upload DNA sequence to online database GenBank

How is describing a new species controversial

Can modern methods (photography, sound recording genomics replace the need for collection of specimen?

physical records provide info about things not captured by photos

• texture

• chemical properties

• increase reliability

Mass extinctions

Period of very high rate of extinction

• meteor strikes

• volcanic eruptions

• reduction is the rate of speciation

Currently experiencing 6th mass extinction due to human actions

Background extinction rate

Refers to the standard rate of extinction in Earth’s geological and biological history excluding major extinction events

• 1-5 species extinction per year

• current rates 100s or 1000s times higher than background extinction rate

Modern extinction rates

Number of vertebrae species classified by the IUCN Red List

• extinct

• extinct in the wild

• Possibly extinct / critcally endangered

million species per year

Modern species extinction rates are 8-100x higher tahn the background extinction rate and only for vertebrates

• extinction rates higher for amphibians and fish than for other vertebrae groups according to IUCN (more sensitive)

Latitudinal Diversity Gradient

Species richness tends to increase from the poles towards the tropics

Why are there more species in the tropics than in subtropical, temperate and polar regions?

1. Time and area hypothesis

2. Diversification rate hypothesis

Time and area hypothesis

Tropical regions have existed for a longer time and covers a larger area compared to colder regions

• tropical like climates extended as far as north as the present day London

• more time and space for species to evolve and diversify over generations

• warm climate stayed relatively stable and undisturbed

• over time build DNA mutations which help them adapt

Time and area hypothesis (Weakness)

• Few tropical species date back to the Cenozoic era (66 million yrs ago)

• Experts say the average species lasts only about 15 million years before going extinct

• The Latitudinal Diversity Gradient cannot be explained by being stable all along

Diversification rate hypothesis

Species in the tropics evolve and diversify

Temperate and polar regions time and area hypothesis

Experienced multiple waves of glaciers during the Pleistocene era

• made the survival of species harder

• many modern temperate species descended from tropical ancestors that have moved into temperate zones as glacier retreated

Diversification rate hypothesis

New species form faster and go extinct slower in tropics

• Diversification rate higher in tropical regions

• Stable mild climate (tropical climate) lets species specialize more

• do not have to spend a lot of energy to survive in climate

Intense interaction between species could speed up evolution

• 2 species share same environment and compete for same resources

• After many generations, this competition can lead to new adaptations and sometimes new species —> co-evolution

Higher temperatures increase metabolism

• speed up evolution

• shortening generation times

• increasing mutation rates

More genetic diversity and species form faster

Why do these theories most likely NOT stand alone?

Other factors not discovered yet

Importance of biodiversity for humans (AID)

Ecosystem services are the benefits people obtain from ecosystems:

1. Direct services

• Obtained through removal products in nature

• e.g wood, fish, water, medicine

2. Indirect services

• Indirect benefits by healthy ecosystems regulating the environment which provides benefits to human

• e.g water filtration (mangroves), carbon sequestration (forests)

3. Aesthetic or ethical benefits from biodiverse ecosytems

• sunsets, waterfalls, mountain

• inspire writers and conservation efforts

• indegenious cultures hold strong ethical values to the protection of certain species

Large populations of animals, plants and microorganisms contain a wider variety of genes within their gene pool

• helps species adapt to environment

Higher genetic diversity is linked to higher resilience of a species to change in the environment

• rice in SEA withstand flooding —> food security in changing climate

Gene pool

complete set of genetic information found within a population of species

• include different genes and variations known as alleles

Small gene pool commonly caused by

Inbreeding - mating between closely related individuals, less genetic diversity —> hard to adapt —> increase extinction risk

Endemic species

A plant, animal or other organisms whose natural geographic range is confined to a single specific area, found nowhere else in the world

• e.g koalas

What are biodiversity hotspots

A region with very high concentration of endemic plants and wildlife that are heavily threatened by human activity

To qualify as a biodiversity hotspot what are the criterias?

High species richness of endemic vascular plants

• at least 1500 species of flowering plants and conifers

• contain specialised tissues for transporting water and nutrients

• excludes non-flowering plants like mosses and liverworts

Experienced significant loss of its natural vegetation

• at least 70-75% loss

• destroyed or altered due to human activities

Malaysia biodiversity hotspots: Sundaland

1. Sundaland

• Borneo

• Peninsula Malaysia

• Western Indonesia

2. Philippines

• Archipelago with highly fragmented islands

• unique species found nowhere else

3. Wallacea

• Transitional zone between asia and australia include sulawesi and lesser sunda islands

4. Indo Burma (Thailand, Cambodia, Vietnam etc…)

• freshwater biodiversity

• forest ecosystem

Food Chain, Food webs and Trophic cascades

Food Chain

Simple linear diagram showing energy flow using arrows to point from one organism to another showing who eats whom

• Primary producers (1st trophic level) to quaternary consumers

Food Web

Descriptive diagram combining multiple food chains

• feeding relationships

• transfer of food energy within a community

Trophic Cascades

The number of steps an organism is from the start of a food chain

• shows how the removal of a top predator has ripple effects in the food web impacting the whole ecosystem

Why is energy transfer through food chains not 100% efficient? Why do food chains only have a few levels?

• At each trophic level, energy is lost mainly due to metabolic processes and heat loss

• Energy becomes too limited to support additional consumers

Autotroph

Make own food using sunlight from photosynthesis

Why can one animal occupy several trophic levels

Diverse diet

Trophic cascades

Involves the addition or removal of top predators (tertiary or quaternary) leading to changes in the abundance of consumers and producers throughout a food web, potentially leading to multiple indirect environmental impacts

Example of trophic cascades Predator-Herbivore-Plant Dynamic

Otters, kelp forests and sea urchins in the pacific ocean

• Kelp forests: shallow seas with high density of kep

• Sea urchins herbivores that feed on kelp

Without predators sea urchins population grows unchecked leading to overgrazing and kelp loss

• otter control their population

Cross Boundary Subsidy Cascades

Chain reactions in a food web caused by resources entering an ecosystem from a different habitat, altering the feeding relationships and interactions among organisms

E.g Wild boars that feed on nearby agriculture land like palm oil plantations

• Natural predators are tigers

Benefit of cross boundary subsidy cascades (wild boars)

Gain extra high energy food supply

• boost survival —> increases reproduction

• construct nest before giving birth using shrubs but in rainforest there are few understory shrubs so boar snap or uproot small tree saplings —> nests

• cause natural disturbance to soils by rooting for food and wallowing in mud to remove parasites

• Effect growth and survival of saplings —> alter forest stucture overtime

Wild boars and Palm oil plantations

Population of wild boars increase with increase in palm oil fruits

• increase damage of tree seedlings

• reduce tree reproduction

• alter forest structure can be seen more than 1km of the forest

RIPPLE EFFECT

What happens if tigers are removed

One of the top predators left with leopards and jaguars

• insufficient predation pressure

• wild boar population grow unchecked

• food web unbalanced