New species
Lesula
13 September 2012
A new species of monkey has been identified in Africa, only the second time such a discovery has been made on the continent in 28 years. The Lesula, which received its scientific name today, has an uncanny resemblance to a more well-known species of monkey: humans.
Take a look at this video clip:
New monkey species discovered -
Its long pointed nose and large eyes give it a striking appearance.
The monkey, who has been given the scientific name Cercopithecus lomamiensis, was first seen in the forests of Congo in 2007.
Scientific research
But a strange-looking monkey cannot simply be designated as a new species. That’s not how science works. In the years that followed this discovery, a collaborative team of experts spent time studying the Lesula from top to toe. When compared to a similar monkey called the owl-faced monkey, they noticed small but statistically significant differences in the size of the eye sockets and in the anatomy of the skull.
What proof is used by scientists to classify organisms into different species? Which characteristics suggest that species are related? How do scientists construct a phylogenetic tree?
These are the topics discussed in this module.
In the final step you will also construct a phylogenetic tree yourself.
For starters
Refresher test
1 Evolution is a theory about ... the origin of life on Earth
how living things changed after their origin.
2 Populations evolve in a direction that is ...
entirely due to chance
not entirely due to chance.
3 Which statement is true?
Evolution always leads to improvement.
Evolution can lead to improvement but this is not always the case.
4 Evolution is about ...
changes in individuals
changes in populations.
5 Which statement is true?
Humans are at the end of their evolution – mankind is no longer evolving.
Mankind is still evolving.
6 Which statement about evolution is true?
When circumstances change, an organism can change its characteristics and pass them on to its offspring.
When circumstances change, the individuals that are best adapted will have a better chance of survival and produce more offspring.
7 Mutations can be passed on …
only by body cells.
only by sex cells.
by body cells and by sex cells.
8 Which statement is true?
Evolution is most rapid when the environment changes.
The rate of evolution is determined by the rate at which mutations occur.
9 Which statement is true?
"Survival of the fittest" refers to the survival of the healthiest and strongest animals.
"Survival of the fittest" refers to the survival and reproduction of the organism that is best adapted.
10 Which statement is true?
All characteristics of organisms are adaptations.
Many characteristics of organisms developed by chance.
Final product - Assessment
Final product
At the end of the module you will formulate a hypothesis about the genetic relationships and shared ancestry within a genus of lizards on the Dutch Antilles.
Assessment
You will discuss the result with your teacher.
Goals - Concepts
Learning goals
- describing that species are groups of individuals that can be isolated from one another in terms of reproduction;
- explaining that species develop through reproductive isolation;
- explaining how genetic relationships and shared ancestry of species can be depicted in the form of a cladogram (phylogenetic tree).
Subconcepts
Species, genus, phylogenetic tree, homology, analogy, characteristic, reproductive isolation, speciation.
Skills:
A5 Investigating
A13 Reasoning in terms of evolution
Method
Format
Work through steps 1 to 5 individually or in groups of 2.
Add to your own answers where necessary.
Step 6 is an assignment to be completed in groups of 2.
You will discuss the result of the assignment with your teacher.
Materials required
- Island map -
- Data table -
- Anolis lizard icons -
- Phylogenetic tree -
Time required
For this module you will need about 8 hours.
GET TO WORK!
Step 1
Phylogenetic trees
It is not known how many different species of organisms currently inhabit the earth. To date, biologists have described about 1.8 million different species, but the actual figure is thought to be far higher.
Oceans, rainforests and coral reefs in particular are thought to contain many undiscovered species. Although there are enormous differences between all these different species, there are also a number of striking similarities.
Assignment 1
What are the similarities between living organisms?
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Assignment 2
Biologists have tried to organise all these millions of species using
a system of classification. Read the information in your textbook about Linnaeus, classification and binomial nomenclature (species name and genus name).
Then take a look at the following video clip for an overview:
New animal species 2012 -
Perhaps you have a household pet.
Have you ever thought about your pet’s ancestors?
The phylogenetic tree shown here on the right shows dog ancestry.
But how are you supposed to read such a phylogenetic tree?
Source: bio.miami.edu
Assignment 3
A phylogenetic tree is used to depict genetic relationships.
Write down the following words inthe correct places in the figures.
Ancestor – common ancestor of B and C - common ancestor of A, B and C – unique ancestor C – branching off of new species
Assignment 4
Imagine you have found five different species with a single common ancestor:
A, B, C, D and E.
How might they be related?
Draw four possible phylogenetic trees.
Assignment 5
Take look at the following phylogenetic tree.
Can you say that humans are descendants of chimpanzees?
yes
no
Can you conclude from this phylogenetic tree that humans and chimpanzees share a common ancestor?
yes
no
Step 2
Which characteristics can you use?
In order to build a phylogenetic tree, biologists collect data about characteristics.
Such characteristics can be related to structure,to behaviour or to DNA. Not all characteristics are equally suitable for determining genetic relationships.
Assignment 1
Which characteristics are suitable?
Which are less suitable? Write them to the correct column.
Fur colour - Number of vertebrae - Presence of wings - Presence of gills - Lays eggs - Number of flowers - Number of petals per flower - Type of locomotion - Number of limbs - Body weight
Suitable / Less suitable…………………………………………………………………………………………… / ……………………………………………………………………………………………
…………………………………………………………………………………………… / ……………………………………………………………………………………………
…………………………………………………………………………………………… / ……………………………………………………………………………………………
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Biologists need to sort the different species into groups.
It is important that they know which characteristics animals have in common and which characteristics make them different to one another. Scientists can represent these evolutionary relationships by constructing phylogenetic trees, also known as cladograms.
Each 'branch' of the tree contains all species that share a common ancestor.
Take a look at this video clip:
Evolution in 5 minutes -
Assignment 2
Amphibians, turtles, lizards, crocodiles, birds and mammals all have four limbs. Modern-day snakes do not, although they sometimes still have vestigial limbs.
1 These four limbs developed at a certain point during evolution.
Which of the 5 lines in the figure correctly indicates this point during evolution?
2 Is having four limbs a characteristic that is suitable for making a distinction between amphibians and reptiles?
yes
no
3 And can it be used to make a distinction between fish and amphibians?
yes
no
Step 3
Homology and analogy
Do structural similarities always mean that species are related?
Take a look at this video clip:
Analogy/homology -
In summary:
Body parts with similar structure and function that developed separately during evolution are said to be analogous. Body parts derived from the same basic plan and originally having the same function, but that developed different shapes and functions as a result of changing circumstances and evolution, are said to be homologous.
Assignment 1
Are the following body parts homologous or analogous?
Wings of a bird and a bat
analogous
homologous
Wings of a dragonfly and a butterfly
analogous
homologous
Wings of a butterfly and a bird
analogous
homologous
Fins of dolphins and arms of humans
analogous
homologous
Fins of sharks and dolphins
analogous
homologous
... is the result of sharing a common ancestor and therefore sharing the same structure.
analogous
homologous
... is the result of a species adapting to certain circumstances or to a way of life.
analogous
homologous
Assignment 2
Take a look at the figure showing specialised insect legs.
Are the different legs homologous or analogous?
analogous
homologous
Step 4
Theory of evolution
Although Darwin is generally considered to be the founder of the theory of evolution, he was not the first to have such ideas about life on earth.
Sometime earlier the Frenchman Lamarck (1744-1829) proposed a theory regarding the gradual changes observed over time in different species. However, it was Darwin (1819-1882) who made convincing arguments for the causes of such changes, thereby providing the basis of the current theory of evolution.
Want to know more? All of Darwin's works can be found online. darwin-online.org.uk/
Assignment
Write a summary about Darwin's theory of evolution.Make sure you include the following words: struggle for life, survival of the fittest, natural selection, adaptation.
You can use your textbook, the videos provided on page 2 and other sources on the Internet.
But make sure you know where the material comes from: who has put it online and for what purpose?
Sources
Evolution -
Origin of Species by Charles Darwin -
Step 5
Speciation
Natural selection leads not only to changes within one species but also to the development of new species, a process known as speciation.
Organisms that belong to a single species share very many similarities.
They can also interbreed and produce fertile offspring.
When biologists talk about a certain species, they are usually referring to the population in a certain area. After all, it is almost impossible to study all the individuals of a single species. Such populations are separated from other populations of the same species.
Reproductive isolation
The process of speciation requires reproductive isolation.
This means that groups of individuals can no longer interbreed.
Take a look at this video clip:
The basics of reproductive isolation -
In summary:
1 Pre-zygotic reproductive isolation = factors that prevent egg cells and sperm cells meeting.
- geographic isolation (physical barrier, e.g. river or ridge)
- temporal isolation (mating at different times of the year)
- behavioural isolation (reproduction hindered due to courtship behaviour)
- mechanical (incompatible reproductive structures)
- gametic (incompatible gametes, fertilisation not possible)
2 Post-zygotic reproductive isolation
- genetic incompatibility (the zygotes do not develop, unworkable hybrids)
- hybrid sterility (hybrids survive but are infertile)
- the hybrids have a limited lifespan
Pre-zygotic
prior to copulation
Pre-zygotic
after fertilisation
Assignment
Look for examples of at least four different forms of reproductive isolation in plants and/or animals. Exchange your answers with a classmate.
Step 6
Anolis
Saba is home to a very special species of lizard, the Saban Anole (Anolis sabanus). This very small anole is the island’s only true endemic species, meaning that it is found nowhere else in the world but Saba.
The Saban Anole may be considered rare because of its very limited geographical distribution, but within Saba it is very common.
Assignment
In this final assignment you will study the lizards of the genus Anolis that are found on the Greater Antilles (Cuba, Hispaniola, Puerto Rico and Jamaica).
You will formulate and test a hypothesis about the genetic relationships between the Anolis lizards and their shared ancestry.
Getting started
Colour code the islands on the map so that each island is a different colour.
Looking for patterns
- Look closely at the data table to determine the type of information that it shows (body shape, habitat and island).
- Look at the pictures of the 21 lizards on the ‘Anolis lizard icons’ worksheet.
1. Can you see the differences between the 6 different types of body shapes?
Give each different body shape its own symbol (e.g. §, Ω, ∆) and write these symbols next to each of the lizards on the worksheet.
Cut out all the lizards and glue each lizard icon, with its symbol, in the correct place on the map.
2. What patterns do you see between the type of body shape a lizard has and the habitat it lives in?
Does this pattern exist on all islands?
3. Which lizards do you think are more closely related:
- those that live on the same island but in different habitats, or
- those that live on different islands but have the same body features and live in the same type of habitat?
4. Write two alternative hypotheses about how these lizards might have speciated/evolved on and between these islands.
5. How could you test your hypotheses?
Testing your hypotheses
- You decide to test your hypotheses using lizard DNA to create a phylogenetic tree.
Download the results of the DNA evidence:
- Colour the name of each animal in the phylogenetic tree the same colour as the island the lizard is from. Write down the symbol for body shape after each animal's name.
6. Look carefully at the phylogenetic tree for the patterns that exist.
7. Now answer question 3 again. Explain your answer using an example.
8. How could fossil evidence help you test your hypotheses?
9. How do think the lizards could have gotten from one island to another?
10. Animal number 18 stands out from the rest.
How might you explain this animal's position in the phylogenetic tree?
Anolis sabanus
Let's now go back to the lizard on Saba, Anolis sabanus. Study its characteristics to find out where it fits in with the other Anolis lizards.
Discuss this assignment with your teacher.
Sources of this assignment:
StudioBiologie | Module New spieces