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When was the Cambrian explosion? and why is this time significant?

570 million years ago. This is when multi-cellular life takes off and all major body plans of animals are established.


When was the Burgess shale formed?

540 million years ago.


Why is the Burgess shale significant?

1) Some of the best fossil preservation of soft bodied organisms. 2) Showed that complex life was present in earths early stages which defied the theories at the time.


Why is the fossil record significant?

It allows us to view evolutionary change over time and examine speciation and extinction.


What is a draw back to the fossil record?

Soft bodied organisms do not preserve as well as hard bodied ones so there are gaps in the history.


What is perpetual change?

One of Darwin's theories that the living world is always changing with hereditary passed from past to present life.


What is evidence of perpetual change?

The fossil record because you can trace evolution and hereditary in it.


What is common Descent?

Another of Darwin's 4 theories that states all forms of life came from a common ancestor through a branching of linegaes.


What is adaptive radiation?

The production of ecologically diverse species from a common ancestor.


What is evidence to support Darwin's theory of common descent?

Homology, This is the idea that animals share similar structures despite diverse modifications. E.g humans and bats both have finger like structures. E.g bat wing, human arm and fin diagram.


What is homology?

The idea that animals share similar structures despite diverse modification.


What is Darwin's theory about multiplication of species?

The idea that evolution creates new species by splitting older ones. Evidence of this is allopatric speciation where 1 species of a population is separated by a physical barrier and becomes 2 species (or more).


What is Ontogeny?

The history of the development of an organism. Similar to homology. E.g fish, human embryos look remarkably similer despite being very different spcies. Also helps to prove common descent.


How does natural selection occur?

It occurs because of genetic variation e.g some individuals will have weaker genes or defects that allows them to be selected against. Excess offspring are produced, this excess offspring forces competition.


What happens when natural selection occurs?

It creates new adaptions and can possibly create new species if conditions are right. ( Speciation).


What are RIMs?

Reproductive Isolating mechanisms.


What are the 2 types of RIMs?

Prezygotic and Postzygotic.


Give examples of prezygotic RIMs

Habitat, timing or temporal, behavioural and physical. Habitat: Animals live in different places. Temporal: animals are breeding at different times. Behavioural: Different breeding behaviour e.g different sound communication or courtship. Physical: The key doesn't fit the lock, incompatable structures.


What is a postzygotic RIM?

Offspring are produced but zygotes are weak non-viable or sterile. E.g Tiger trout.


What is Gradualism?

Darwin's theory that physical changes among species are small and accumulate over time rather then occuring in one generation. This has been partially proven but doesn't fully explain all examples.


What is natural selection?

The idea that organisms accumulate favorable characteristics over time based on their Enviroment. (Adapations).


What is phyletic gradualism?

Darwin's idea of gradualism describing slow gradual change on a geological time scale ( natural looking phylogenetic tree). Thought the be incorrect because it does not explain extincting events .


What is punctuated equilibrium?

Contradicts the phyletic gradualism model. It shows morphology changes as short bursted events followed by very long periods of little change.


What are the types of natural selection?

1) Directional: A shift in the mean population e.g light skinned slug is favored over dark and medium slugs. 2) Stabilizing selection e.g medium skinned slugs are selected for and dark and light skinned are selected aginst. 3) Disrupted selection light and dark skinned slugs are favored against medium skinned slugs.


What is sexual selection?

This is when traits are developed in order to be more competitive when selecting mates. There are male combat structures e.g antlers horns, they are costly but without them chance of reproduction is small. Female choice plays the other part males develop colors, calls etc to attract them but in turn makes them more easy targets for predators.


What is are adaptive radiations?

Speciation gone crazy e.g Darvin's finches started as one species and became 14 species.


What was the permian extinction and when did it happen?

250 million years ago 90% of marine invert species went extinct.


when was the cretaceous extinction?

65 million years ago (Dinosaurs dead)


What is a consequence of mass extinctions?

It opens the door for massive adaptive radiations of the remaining organisms because there was vast amounts of ecological space avaliable to thrive.


Name 6 major innovations in animal body plans.

1) Multicellular organisms (Poriferia). 2) True Tissues (nidarians) 3). Animal symmetry. 4) Germ layers. 5) Body cavities (devloped from coelom). 6) Early embryonic development


What is cephalization?

The concentration of sensory structures at the anterior (front) of the animal. Normally correlates with bilateral symmetry.


What are stereo sensory structures? Which were the first organisms to develop them?

Paired sensory structures. First to have them were the platyhelimintheus (flatworms)


What are blastomeres?

The smaller cells that are created when a zygote undergoes clevage.


What do RNA proteins do?

They exist in cytoplasm of cells and determine what type of tissue that cell will become. E.g muscle, nerve etc


What is a Blastula?

A hollow fluid filled ball of many blastomeres which are created by clevage. The fluid filled cavity is called the blastoceol.


What is Gastrulation?

This is when a blastula becomes a gastula by rearranging into into either 3 germ layers or 2 e.g (diplopastic: radial symmetry or Triploblastic: Bilateral Symmetry). The germ layers are endoderm, ectoderm and mesoderm.


What is the blastocoel?

The fluid filled cavity of the blastula.


What does diploblastic mean?

The animal has only 2 germ layers. Ectoderm and endoderm. Animals with radial symmetry have 2 germ layers (cnidarians)


What does Triploblastic mean?

The animal has 3 germ layers. Bilateral animals are triploblastic.


What are the three germ layers?

Endoderm, Ectoderm, Mesoderm.


What animals lack a zygotic clevage pattern?



What is regulative development and when does it occur?

During early gastrulation if blastomeres are separated from the blastula they can individually regulate their development into an embryo. Regulative development occurs with radial clevage.


What is mosaic development and when does it occur?

During Spiral clevage if blastomeres are separated


What is the 4d cell? and when is it created?

During spiral clevage around the 29th blastomere, a blastomere is formed called 4d that becomes the mesoderm.


What is a gastrula? and when is it formed?

A gastrula is formed when a blastula develops germ layers during gastrulation. (either 2 or 3).


What is an incomplete gut/how is it formed.

An incomplete gut forms when diploblastic organisms (radial symmetry) undergo gastrulation and a gastrula is formed with only 2 germ layers.


Name all germ layers

Endoderm, ectoderm, mesoderm.


Name all the parts of a Gastrula.

Endoderm, ectoderm, Blastocoel, Blastopore, gastroceol.


What do the gastrocoel and the blastopore become respectively?

The gut, if an incomplete gut the blastopore forms the anus and mouth, if complete gut forms it can become the anus or the mouth. If it becomes the anus a secondary mouth forms and vice versa.


What are the three kinds of body types that develop with a complete gut?

Pseudocoelomate: Mesoderm lines the outer edge of blastocoel. Acelomate: Mesoderm completely fills the blastocoel. Ceolomate: The mesoderm fills the blastocoel and then a cavity forms inside the mesoderm.


Give examples of pseudocoelomate, acoelomate, and ceolomates

Pseudo: Nematodes (roundworms). Acoelomate: Gastrotrich ( hairybacks). Ceolomate: Annalids (earth worms)


What are the three types of Eukaryotic cells?

1) Ciliates (filter feeding). 2) Flagellates (locomotion/ parasites). 3) amebas (goo predators can have tests aka shells)


what are the 2types of reporduction for eukaryotes and protozoa?

Asexual: Binary fission or multiple fission (protozoa) and Sexual:


What is encystment?

When protists go into a dormancy state protected by a durable covering called a cyst. (outside hosts)


What is excystment?

When protists exit their dormancy cyst. (Inside hosts)


What is trypanosoma brucei known for?

It cause African sleeping sickness


What organism cause afican sleeping sickness?

Trypanosoma brucei via tetse fly vector


What causes beaver fever?

Giardia duodenalis.


What are trophozoites?

These are the growth forms of giardia that emerge from cysts in the host's bowels. 2 per cyst then massive binary fission occurs.


What are reservoir hosts?

Secondly hosts that can spread giardia (binary fission inside them) or other protozoans but are not harmed by them.


What are ciliophora aka cilicates? Give an example of one

Complex uni-cellular aquatic organisms. Paramecium


What are trichocysts? and toxicysts

Defense mechanisms in ciliates and predatory weapons respectively in paramecium.


What is the difference between trichocysts and toxicysts?

trichocysts are for defense toxicysts act similer to nematocytes and used for feeding via paralyzing toxins..


What is conjugation?

Two single celled animals become one to exchange genetic material and then separate again.


What is malaria caused by?

Plasmodium vivax


What type of mosquito is the vector for plasmodium vivax?

A female Anophles mosquito


What is schizogony?

Asexual reproduction Multiple fission. ( nucleus splits and the rest of the cell splits into as many pieces).


What are merozoites?

These are the renamed sporozoites once they break free of liver cells.


What is a apical complex?

The organelle that merozoites use to rupture and enter red blood cells.


What are trophozoites in regards to plasmodium vivax?

Trophozoites feed in red blood cells and produce more merozoites


What are sporocysts?

The form in which that plasmodium vivx is injected into the host by the anepheles mosquito.


What are ookinetes?

When plasmodium vivax gametocytes form a zygot inside the anepheles mosquito it matures into ookinetes in the stomach.


what are oocysts?

The cyst form that ookinetes form on the mosquito stomach lining.



sexual reproduction that creates sporozoites or spores.