Apple Airport Card

Yesterday I installed Ubuntu on my Intel-based iMac. However, after the installation, it turns out that Ubuntu is unable to utilize the internal airport extreme card for WiFi. How can I fix this?

The command lshw -C network tells me:

*-network                 
   description: Ethernet interface
   product: MCP79 Ethernet
   vendor: NVIDIA Corporation
   physical id: a
   bus info: pci@0000:00:0a.0
   logical name: enp0s10
   version: b1
   serial: 00:25:4b:b1:8f:e2
   size: 100Mbit/s
   capacity: 1Gbit/s
   width: 32 bits
   clock: 66MHz
   capabilities: pm msi bus_master cap_list ethernet physical mii 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
   configuration: autonegotiation=on broadcast=yes driver=forcedeth driverversion=0.64 duplex=full ip=192.168.0.27 latency=0 link=yes maxlatency=20 mingnt=1 multicast=yes port=MII speed=100Mbit/s
   resources: irq:27 memory:93586000-93586fff ioport:21e0(size=8) memory:93589000-935890ff memory:93589300-9358930f
*-network
   description: Network controller
   product: BCM4322 802.11a/b/g/n Wireless LAN Controller
   vendor: Broadcom Limited
   physical id: 0
   bus info: pci@0000:04:00.0
   version: 01
   width: 64 bits
   clock: 33MHz
   capabilities: pm msi pciexpress bus_master cap_list
   configuration: driver=b43-pci-bridge latency=0
   resources: irq:18 memory:93200000-93203fff