1. A 3.1 HL Diversity of organism.ppt tx

IB Biology

1. A 3.1 Diversity of Organism (AHL) “What is a species?” “What patterns are seen in the diversity of genomes within and between species?”

2. A3.1.12 AHL Difficulties applying the biological species concept to asexually reproducing species and to bacteria that have horizontal gene transfer The biological species concept does not work well with groups of organisms that do not breed sexually or where genes can be transferred from one species to another. A3.1.13 AHL Chromosome number as a shared trait within a species Cross-breeding between closely related species is unlikely to produce fertile offspring if parent chromosome numbers are different. A3.1.14 AHL Engagement with local plant or animal species to develop a dichotomous key   A3.1.15 AHL Identification of species from environmental DNA in a habitat using barcodes Using barcodes and environmental DNA allows the biodiversity of habitats to be investigated rapidly. Learning Objectives

3. Difficulties applying the biological species concept If members of a species interbreed sexually their traits are remixed. This Dandelions ( Taraxacum officinale ) only reproduce asexually by mitosis. Offspring is identical to the parents – they are clones. All offspring from asexual reproduction are clones to their parents without any genetic variability. Because clones don’t interbreed with other clones there is no mixing of traits and they are considered to be separate species according to the biological species concept . Over time thousands of different clones develop .

4. Difficulties applying the biological species concept https://www.news-medical.net/life-sciences/Horizontal-Gene-Transfer.aspx Bacteria can do horizontal gene transfer, where genes from one bacterial species might by transferred without sexual reproduction to another bacterial species – and this might even happen between distantly related species. Different species usually don’t interbreed naturally but stay reproductively isolated . Why does this “behaviour” not apply to bacteria, and why is it therefore difficult to apply the species concept?

5. Difficulties applying the biological species concept There is so much gene transfer that it is unclear whether bacteria actually should be considered as a species according to the species concept. Maybe the species concept should not apply to bacteria? Horizontal gene transfer is how bacterial resistance can move from one bacteria to another, so species don’t really stay separate from each other.

6. Chromosome number as a shared trait within a species https://bigcatrescue.org/liger-facts/ Members of the same species hav e the same chromosome number. Cross-breeding between closely related species is unlikely to produce fertile offspring if parent chromosome numbers are different. The liger is actually fertile, as it inherited 19 chromosome from both of the two different parents.

7. Chromosome number as a shared trait within a species https://www.britannica.com/animal/liger

8. Horses and donkeys are different species, with different numbers of chromosomes. Of the two hybrids between a female horse and a male donkey, a mule is easier to obtain than a hinny (the offspring of a male horse and a female donkey). All male mules and most female mules are infertile. http://www.ponderweasel.com/wp-content/uploads/2015/07/difference-donkey-horse-mule.jpg Chromosome number as a shared trait within a species Interbreeding of different members of a species results in infertile offspring.

9. Has it got legs? Has it got 6 legs? Has it got 2 pairs of wings? Has it got a shell? No Yes No Spider Yes No snail earthworm Start here Yes Yes No wasp housefly 1 Has legs………….............. Go to 2 Has no legs……................Go to 4 2 Has 6 legs …………………...Go to 3 Has 8 legs …………………….Spider 3 Has 1 pair of wings……....Housefly Has 2 pairs of wings………Wasp 4 Has a shell…………………….Snail Has no shell…………..……..Earthworm A couplet consists of two descriptions which should represent mutually exclusive choices (often it is a particular combination of characteristics that determines the difference). (usually written) device constructed from a series of highly organized statements arranged into couplets . Dichotomous key Each couplet only expects two answers to each question (YES or NO).

10. Dichotomous key Know the structures in order to develop a good key!

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14. Dichotomous key You will be working in groups of 3. Download the App Pl@ntNet from the AppStore or from the Google Playstore in order to be able to identify the plant leaves you are collecting. C ollect 4 plant leaves (each student!) . Bring your leaves to school (ideally they should still be alive…) . Identify each leaf with the App and write down the name on a piece of paper . Stick the leaves on the top of an A3 poster paper and number them from 1 – 10. Do not write down the species name underneath – that needs to be identified . Make yourself familiar with the terminology for the structural and anatomical features (leaf shapes, margins, venation…) of your leaf/plant. Now create a dichotomous key ! O n ce finished, this key will be passed on to the students from another group – if they identify all leaves correctly, they will win that battle! If you identify their leaves correctly, you win the competition!

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18. https://www.sciencelearn.org.nz/images/5114-creating-a-dna-barcode Identification of species from environmental DNA DNA barcodes are short sections of DNA from one gene distinctive enough to idenify a species. The barcode allows scientists to identify species from small cell samples. Using collected samples from environmental DNA (e.g. from animal tracks, tree scratches etc) it is now possible to identify species. Barcodes are established and stored in databases by DNA extraction and sequencing.