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Pond Water. Lab 2 BIO 101. Evolution via natural selection. What would happen if all of the trees and dinosaurs were the same size?. Individual variation is necessary for natural selection to occur. What would happen if all the dinosaurs produced just one offspring?.

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Pond Water

Lab 2

BIO 101


Evolution via natural selection


What would happen if all of the trees and dinosaurs were the same size?


Individual variation is necessary for natural selection to occur.


What would happen if all the dinosaurs produced just one offspring?


Differential fitness is necessary for natural selection to occur.


What would happen if offspring never resembled their parents?

Parents:

Offspring:


Traits must be heritable for natural selection to occur

Parents:

Offspring:


Conditions required for natural selection to occur:

Individual variation: members of a species differ in their characteristics

Mode of inheritance: parents pass on some of their traits to their offspring

Differential fitness:some individuals leave more offspring than others due to their special inherited traits


Classification System


We’ll be looking at all of these!

Protists are everywhere in Eukarya!

“the junk drawer of the eukaryotes”

Ancestral

Eukaryote


We’ll be looking at all of these!

Protists are everywhere in Eukarya!

“the junk drawer of the eukaryotes”

Ancestral

Eukaryote


6 Kingdoms

  • Plants (Plantae)

  • Animals (Animalia)

  • Fungi (Fungi)

  • Eubacteria

  • Archaeabacteria

  • Protista


A constantly changing system…


Euglena- Heterotrophic and phototrophic (can engulf food via phagocytosis, or use sunlight)- Flagellated


Paramecia- Heterotrophic only

- Ciliated- Harbors endosymbiotic green algae that provide food in exchange for protection


Dinoflaggelates


Diatom diversity


Diatom cell wall made of silica


Animals!

  • Hydra (Cnidaria)

    • Baby jellyfish that never become adults.

    • Radial symmetry

  • Rotifers (Rotifera)

    • Wheel animals

    • Bilateral symmetry


A note on symmetry

  • Bilateral symmetry last to evolve, approx. 555 mya.

  • Radial symmetry is older, and contains only corals, sponges and jellies.


Phylum Cnidaria – Hydras (Hydra)

  • Two tissue types, no organs – no anus!

  • Includes: corals, jellies, sea anemones, and Portuguese men-of-war. (9000+ spp!)

  • Most species are marine, few freshwater spp.

  • Generally two body forms present in the life cycle:

    • Umbrella-like, free-swimming stage (called a medusa)

    • Cylindrical, attached or stationary form – often grows into colonies of individuals (called a polyp)

  • Hydra exist only as polyps


Random cool stuff about Hydras

  • They are capable of morphallaxis

    • Regeneration into entirely new individuals

    • Because of this, they might be biologically immortal.

  • Nematocysts

    • Cnidocytes are the stinging cells

    • Explosively discharge harpoon

    • Contain neurotoxins which immobilize prey

  • Two body layers

    • Epidermis on the outside

    • Gastrodermis on the inside

  • They’re hermaphrodites

  • Some have symbiotic relationships with algae

Adult medusa


Phylum Rotifera- Rotifers

  • Very small animals – most 0.1 – 0.5 mm in length

  • Most common in freshwater, though some salt water species

  • Important part of freshwater zooplankton, being a major food source and many species contributing to decomposition of organic matter.

  • Pharynx contains tiny, calcified, jaw-like structure called trophi


Other neat things about rotifers

  • They have “cement glands” which excrete an adhesive to hold them down.

  • They have an anus!

  • They have a brain! (hydra have nerve webs)

  • They can reproduce sexually or parthenogenetically – development of an embryo without being fertilized (like some reptiles and fish) (also, they’re dioecious– only males and females, no hermaphrodites)

  • Resting eggs – eggs which develop into zygotes that can survive very harsh conditions (like winter)


Think about…

  • Morphological characteristics

  • Ecology of the organism

  • How does the organism get around?

  • What role do they play in the ecosystem?

  • Do they have any economic value?

  • Where do they live?

  • Don’t know the answer?? It’s probably a great research question! Ask me about it.


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