animals and environment 199103

Darwin and Wallaces 2 main points

1. organisms presently inhabiting the earth are dependents of ancestral species - i.e they evolved

2. Proposed a logical mechanism for the evolutionary process, natural selection

1st point - descent with modification

evolution explains life unity and diversity

2nd point- natural selection

provides a mechanism for adaptive evolution

is the differential success in reproduction which results in certain alleles being passed onto the next generation in greater proportions

Carolus Linnaeus

father of taxonomy (classing things) and binomial nomenclature (naming things)

Georges Cuvier

Largely developed paleontology, the study of fossils. Advocated catastrophism (events in past are different to what they are now) opposed idea of evolutionary change.

James Hutton

Gradualism: Earth's geologic features could be explained by gradual mechanisms currently operating in the world

Charles Lyell

Uniformitarianism - mechanisms of change are constant over time

Lamarck

Proposed theory that organisms pass on traits they acquire in their lifetime. (Incorrect) i.e. Scars but also thought that species evolve through use and disuse of acquired traits.

Adaptation

behavioural and inherited characteristic that increases an organism's chance of survival

Phylogeny

The evolutionary history of a species or group of related species- shows evolutionary relationships

binomial nomenclature

Classification system in which each species is assigned a two-part scientific name. the first part is called the binomial (the genus) the second part is called the Epithet (unique to each species within the genus)

hierarchal classification

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

phylogenetic tree

A branching diagram that represents a hypothesis about the evolutionary history of a group of organisms.

Homologies

morphological similarities between organisms based on descent from a common ancestor. (be careful not to confuse with convergent evolution)

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments

analogous structures

Body parts that share a common function, but not structure (same function different ancestor)

clade

A group of species that includes an ancestral species and all its descendants. a valid clade is monophyletic

monophyletic

ALL descendants came from one common ancestor

shared ancestral character

a homologous structure that predates the branching of a clade

gene duplication

one of the most important types of mutations in evolution. increases the number of genes in a genome creating paralogous genes (parlous). duplicated genes can take on new functions by further mutations

Evolution

change in allele frequency overtime within a population

requiers:

1) compétition

2) variation

3) hereditary

4) differential reproduction

it only acts on gremlin mutations (mutations in somatic cells are lost)

cline

a graded change in a character along a geographic axis

scores of genetic variation

1) formation of new alleles (mutations)

2) altering gene number or position

new genetic combination produced (chromosomal mutations, gene duplication)

3)rapid reproduction

4)sexual reproduction

mutation

a change in the nucleotide sequence

population

A localised group of (impeding) individuals that belong to the same species.

neutral theory

The hypothesis that much evolutionary change in genes and proteins has no effect on fitness and therefore is not influenced by Darwinian natural selection.

Hardy-Weinberg Equilibrium

null hypothesis- allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences. and idealised population will be in equilibrium

Hardy-Weinberg equation

p^2 + 2pq + q^2 = 1

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection. (natural fluctuation in alleles) e.g bottle necking and founder effect

gene flow

Movement of alleles into or out of a population due to the migration of individuals to or from the population

relative fitness

the contribution an individual makes to the fine pool of future generations, relative to the contribution of other individuals in the population

Stabilising selection

a type of natural selection in which genetic diversity decreases as the population stabilises on a particular trait value (makes high narrow bell curve)

directional selection

shifts complete overall makeup of the population by favouring variants at one extreme of the distribution (moves whole bell curve)

distributive selection

natural selection in which individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle of the curve (make 2 mini bell curves)

fitness coefficient (W)

An expression of the adaptive value of a particular genotype relative to other genotypes. The genotype that produces the most offspring in a given population is assigned a fitness value of 1.0

selection coefficient (S)

a measure of the relative intensity of selection against a given genotype, relative to others in the population.

1-W

artificial selection

Selection by humans for breeding of useful traits from the natural variation among different organisms e.g dogs

sexual selection

A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.

heterozygous advantage

Heterozygous alleles have greater selective advantage than either homozygous condition.

punctuated equilibrium

Pattern of evolution in which long stable periods (stasis) are interrupted by brief periods of more rapid change

Instant speciation

The formation of a new species through autopolyploidy or allopolyploidy. Because the chromosome numbers of the new 'instant' species do not match that of the original species they cannot interbreed.

adaptive radiation

the evolution of a diversely adapted species from a common ancestor upon introduction to new environmental opportunities

heterochrony

Evolutionary change in the timing or rate of an organism's development.

Allometry

the study of the relationship between size and shape. allometric growth is proportioning that helps give the body its specific form.

Paedomorphosis

The retention in an adult organism of the juvenile features of its evolutionary ancestors.

homeotic genes (hox genes)

Genes that determine basic features of where a body part is. specify the anterior- posterior axis and segment identity of metazoan organisms in early embryos

Domains

Bacteria, Archaea, Eukarya

prokaryotes

Bacteria and Archaea are prokaryotes - most are unicellular, Cells lack a nucleus and other membrane- enclosed organelles. have a cell wall.

bacterial cells

contain peptidoglycan, a polymer composed of modified sugars crosslinked by short polypeptides.

Eukaryotes

include protists, animals, plants and fungi. Most eukaryotes are much larger than prokaryotes. eukaryote cells have a nucleus and other membrane-bound organelles such as mitochondria and Golgi apparatus, cells also have a well-developed cytoskeleton that provides structural support.

protists

single-celled or simple multicellular eukaryotic organisms that generally do not fit in any other kingdom (plant, animal, or fungi)

Plants

multicellular, eukaryotic, photosynthetic autotrophs, as are brown, red, and some green algae.

Fungi

Multicellular, eukaryotic heterotrophs that feed by absorption. A kingdom made up of nongreen, eukaryotic organisms that have no means of movement, reproduce by using spores.

Animals

Multicellular, heterotrophic eukaryotes with tissues that develop from embryotic layers. in most cases they need to ingest food.

animal reproduction

sexual - After a sperm fertilises an egg, the zygote undergoes rapid cell division called cleavage

Cleavage leads to formation of a multicellular, hollow blastula

The blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues

autotrope

can generate own food

Phylum: Porifera

sponges;

- sessile (attached at base; don't move);

-lack true tissues and don't have a nervous system

- body with pores

- filter feeders (Water enters through pores into a central cavity, the spongocoel, then flows out a larger opening called the osculum)

- have spicules

- two-layers of the wall of a sponge are separated by gelatinous mesohyl

spicules

Found in sponges, these consist of inorganic materials and support the animal

spongocoel

main cavity in a sponge where water filtered water enters through pores

Choanoflagellates

microscopic aquatic organisms that can alternate between single-celled and multicellular states. DNA sequence data indicate that choanoflagellates and animals are sister groups, with choanoflagellates being the closest single-celled relatives of animals.

radially symmetrical

organisms that are segmented in a circular pattern around a fixed point (have a top and a bottom, but no front or back, or left or right)

Triploblastic

has three germ layers: the ectoderm, endoderm, and mesoderm. All bilaterally symmetrical animals are triploblastic

Ectoderm

outermost germ layer covering the embryo's surface; produces sense organs, nerves, and outer layer of skin

Endoderm

the inner germ layer that lines the developing digestive tube, called the archenteron that develops into the lining of the digestive and respiratory systems

Phylum Ctenophora

comb jellies

- radially symmetrical and diploblastic, animals with true tissues

-distinctive traits, including eight "combs" of cilia that propel the animals through the water

Diploblastic

having two germ layers; ectoderm and endoderm. include ctenophores and cnidarians

lophophore

a crown of ciliated tentacles that function in feeding

Phylum Cnidaria

-radially symmetrical

- diploblastic body plan (that includes a gastrovascular cavity with a single opening that serves as both mouth and anus)

-have true tissues

-carnivores that use tentacles (with cnidocytes) to capture prey

-lack a central brain

-Their muscular system consists of an outer layer of longitudinal fibres and an inner layer of circular fibres

-posses a nerve net with some sensory organs

-basic body plan (with two variations) a sac with a central digestive compartment, the gastrovascular cavity

sessile polyp: adheres to the substrate by the aboral end of its body

motile medusa: has a bell-shaped body with its mouth on the underside- not attach to the substrate but move freely

cnidocytes

Special stinging structures on cnidarians that look like small harpoons. that have Nematocysts

Nematocysts

specialised organelles within cnidocytes that eject a stinging thread

bilateral symmetry

organisms have a dorsal (top) side and a ventral (bottom) side, right and left side, Anterior (front) and posterior (back) end. all have have triploblastic development

Lophotrochozoa

-identified by molecular data

- 3 main sub-phyla, Platyhelminthes, Mollusca, Annelida

Lophotrochozoa

Phylum Platyhelminthes

flatworms:

-Incomplete gut

-No circulatory system

-have a gastrovascular cavity with one opening

-Possess a central nervous system

-Bilateral, triploblastic, acoelomates

-Cephalization

-many are parasites, such as flukes and tapeworms

-use direct exchange nutrients, waste products, and gases with their environment

trematodes

flatworms - flukes

-complex life cycles with alternating sexual and asexual stages

-produce surface proteins that mimic their host and release molecules that manipulate the host's immune system

cestodes

flatworms- tapeworms

-parasites of vertebrates

-they absorb nutrients directly from the host's intestine

The scolex contains sucker (no mouth or gastrovascular cavity)

acoelomates

A solid-bodied ani- mal lacking a cavity between the gut and outer body wall.

Lophotrochozoa

Phylum Mollusca

- are all soft- bodied, and most secrete a hard shell made of calcium carbonate

-all have a Muscular foot, Visceral mass, Mantle

-some feed using a strap-like radula

-many life stages include a ciliated larval stage called a trochophore

- have 4 major classes

Polyplacophora(chitons)

Gastropoda (snails and slugs)

Bivalvia (clams, oysters, and other bivalves)

Cephalopoda(squids, octopuses, cuttlefish, and chambered nautiluses)

trochophore

free-swimming larval stage of an aquatic mollusk

Lophotrochozoa

Phylum Mollusca

Class Polyplacophora(chitons)

oval-shaped marine animals encased in an armor of eight dorsal plates

use their foot like a suction cup to grip rock, and their radula to scrape algae off the rock surface

Lophotrochozoa

Phylum Mollusca

Class Gastropoda (snails and slugs)

Move slowly by a rippling motion of the foot or by cilia.

Most gastropods have a single, spiraled shell that functions in protection from injury, dehydration, and predation

Most are herbivores, but some species use modified radula to feed on prey

Lophotrochozoa

Phylum Mollusca

Class Bivalvia (clams, oysters, and other bivalves)

hell divided into two halves drawn together by adductor muscles

Some bivalves have eyes and sensory tentacles along the edge of their mantle

The mantle cavity of a bivalve contains gills that are used for feeding as well as gas exchange

Most species are sedentary, but some have limited motility

Lophotrochozoa

Phylum Mollusca

Class Cephalopoda (squids, octopuses, cuttlefish, and chambered nautiluses)

active marine predators with beak- like jaws surrounded by tentacles

They are able to immobilise prey with a poison present in their saliva

The foot is modified into a muscular excurrent siphon and part of the tentacles

The shell is reduced and internal or missing in most species, except the chambered nautiluses

Lophotrochozoa

Phylum Annelida

'LITTLE RING'

-coelomates with bodies composed of a series of fused rings

-display metamerism (serial segmentation)

- have two major clades, Errantia and Sedentaria

-Also (except for leeches), they have

chitinous bristles called setae (or chaetae)

that provide anchorage or used for swimming. These may be associated with prominent paddle-like structures called parapodia that function in locomotion.

coelomates

have a true coelom, which is a fluid-filled body cavity completely lined by tissue which is derived from mesoderm

metamerism

Segmented arrangement of body parts

- Most body systems repeated in each

segment (e.g. circulation, nervous, excretion)

-Segments divided internally by a septum

(except in leeches)

Lophotrochozoa

Phylum Annelida

clade Sedentarians

-tend to be less mobile than those in Errantia

-Some species burrow into the substrate, while others live in protective tubes

Tube-dwelling sedentarians often have elaborate gills or tentacles used for filter feeding

-This clade also contains the leeches and the earthworms

Lophotrochozoa

Phylum Annelida

clade Errantians

-is a large and diverse group

-Most members of clade Errantia are mobile marine predators or grazers

-Many errantians have a pair of paddle-like or ridge-like structures called parapodia ("beside feet") on each body segment

-Each parapodium has numerous chaetae, bristles made of chitin

-Parapodia are not unique to this clade

metanephridia

In annelid worms, a type of excretory tubule with internal openings that collect body fluids and external openings that excrete waste from the body.

Ecdysozoa

-defined primarily by molecular evidence but includes animals that shed a tough cuticle as they grow

-includes about 8 animal phyla. only look at the two main (Nematoda and Arthropoda)

Ecdysis

periodic shedding of the cuticle in arthropods or the outer skin in reptiles

Ecdysozoa

Phylum Nematoda

Roundworms

-Non-segmented worms

-Alimentary canal

-No circulatory system

-Longitudinal muscle only

Ecdysozoa

Phylum Arthropoda

-Metamerism

-Tagmatisation

-Jointed legs

-Waterproof exoskeleton & consequences:

• Terrestrial life

• Muscleattachment

• Growth constrained - have to moult

-Huge diversity and numbers (look at Trilobitomorpha, Chelicerata, Myriapoda, Crustacea, Insecta)

Metamerism

Arthropods evolved from a primitive annelid or an ancestor common to both - The ancestor had a segmented body with little differentiation or specialisation of different regions of the body

Tagmatisation

Specialisation of groups of segments

(the grouping of adjacent metameres into larger functional units, tagma, responsible for performing specialised tasks)

Ecdysozoa

Phylum Arthropoda

Diversity Trilobitomorpha

Trilobites

Most primitive known arthropod group

All extinct

0.5 mm - 1 m long

(most 3 - 10 cm)

Possessed biramous (two-branched) limbs

Ecdysozoa

Phylum Arthropoda

Diversity Chelicerata

Horseshoe crabs (Limulus polyphemus)

"living fossils" have changed little in hundreds of millions of years

They are surviving members of a rich diversity of chelicerates that once filled the seas

Scorpions have pedipalps that are pincers specialised for defence and the capture of food. The tip of the tail bears a poisonous stinger.

Web-building spiders are generally most active during the daytime.

Dust mites (far right) are ubiquitous scavengers in human dwellings but are harmless except for those people who are allergic to them.

Ecdysozoa

Phylum Arthropoda

Diversity Myriapoda

a) Millipedes- Class Diplopoda

2 pairs of legs per segment

Herbivores and detritivores

b) Centipedes- Class Chilopoda

1 pair of legs per segment

Carnivores

Both are clearly metameric with tagmosis limited primarily to the head and, in the millipedes, to fusion of adjacent pairs of segments

Ecdysozoa

Phylum Arthropoda

Diversity Crustacea

Crustacea is Latin for 'a crust'

> 42,000 known species

Characterised by having 2 pairs of antennae

Incorporate calcium carbonate in crustacean into their cuticle

Mostly marine

Ecdysozoa

Phylum Arthropoda

Diversity Insecta

insectum, meaning "cut up or divided into segments"

-Evolution of flight (. Enabled insects to disperse widely and rapidly, to colonise new areas, and to exploit new or ephemeral resources, and find mates.)

-Development of a tough exoskeleton (effectively a suit of armour)

-Exoskeleton/cuticle contains protein & chitin (an inert polysaccharide)

-Cuticle hardened by sclerotisation

-Energy efficient jointed limbs rather than hydrostatic skeleton of annelids

-Many are small so many niches are available to them

Deuterostomia

Echinodermata and Chordata. categorized as having deuterostome development In early development